CBSE Class 8 Science Chapter 11 Keeping Time With The Skies MCQs Set 02

Download CBSE MCQs for Class 8 Science: Chapter 11 Keeping Time With The Skies

Access targeted multiple-choice questions for Chapter 11 Keeping Time With The Skies designed to align with the latest CBSE academic syllabus for Class 8 Science. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.

Chapter-wise Objective Questions: Chapter 11 Keeping Time With The Skies

Navigate directly to the 50 objective questions for Chapter 11 Keeping Time With The Skies using the digital viewer below. Each practice set includes verified answer keys, allowing students to instantly cross-check their work and identify areas requiring further revision.

Question: During the waning period of the Moon, which phase directly follows the full Moon shape according to the lunar cycle shown in the chapter?
A. Crescent Moon
B. Gibbous Moon
C. New Moon
D. Waxing Crescent
Show Answer & Explanation

Answer: (B) Gibbous Moon

Explanation:
In the waning cycle, the Moon transitions from full to gibbous (more than half illuminated) before eventually becoming a crescent and finally reaching the new Moon phase.

Question: When observing the Moon at sunrise on consecutive days during the waning phase, how does the Moon's position relative to the Sun change compared to the previous day?
A. It moves farther away from the Sun in the sky
B. It moves closer to the Sun in the sky
C. It stays at the same position
D. It moves perpendicular to the Sun's position
Show Answer & Explanation

Answer: (B) It moves closer to the Sun in the sky

Explanation:
As the Moon wanes and its bright portion decreases, it progressively moves closer to the Sun in the sky until reaching the new Moon position when it appears nearest to the Sun.

Question: In a solar calendar like the Gregorian calendar, why are the day counts distributed unevenly across months (some with 30 days, others with 31, and February with 28)?
A. To make the calendar easier to remember
B. To adjust the total to approximately 365 days while accounting for the Earth's actual orbital period
C. To synchronize with lunar phases
D. To follow ancient Roman traditions without any scientific basis
Show Answer & Explanation

Answer: (B) To adjust the total to approximately 365 days while accounting for the Earth's actual orbital period

Explanation:
The varying month lengths in solar calendars serve a practical purpose—they are adjusted to sum to roughly 365 days, which approximates the time Earth takes to complete one full orbit around the Sun, keeping the calendar aligned with seasonal cycles.

Question: Based on the chapter's explanation of lunar and solar calendars, which type would be most unreliable for predicting when a specific agricultural season will arrive in a given year?
A. Solar calendars
B. Lunar calendars
C. Luni-solar calendars
D. The Indian National Calendar
Show Answer & Explanation

Answer: (B) Lunar calendars

Explanation:
• Lunar calendars have 354 days per year
• Seasons repeat on a 365-day cycle
• Over successive years, lunar months drift away from their original seasons
• This misalignment makes predicting seasonal timing unreliable without external correction

Question: When Meera noticed that the Moon appeared during daytime at the Patang Mahotsav, what does this observation confirm about the Moon's position in its orbit?
A. The Moon was approaching the new Moon phase
B. The Moon was in the gibbous phase or waxing crescent phase positioned away from the Sun
C. The Moon was experiencing a lunar eclipse
D. The Moon's orbit had shifted unexpectedly
Show Answer & Explanation

Answer: (B) The Moon was in the gibbous phase or waxing crescent phase positioned away from the Sun

Explanation:
Visibility of the Moon during daytime occurs when the Moon is not too close to the Sun's glare. During waxing phases or certain gibbous phases, the Moon can be positioned far enough from the Sun to be visible before sunset or after sunrise.

Question: In Activity 11.2, as the observer turns around while holding the ball away from the lamp, the illuminated portion visible changes shape. Which characteristic of the Moon's phases does this activity most directly demonstrate?
A. The Moon's rotation on its axis
B. The relative geometry between the observer, the illuminated source, and the object being illuminated
C. The effect of the Moon's distance from Earth
D. The occurrence of lunar eclipses
Show Answer & Explanation

Answer: (B) The relative geometry between the observer, the illuminated source, and the object being illuminated

Explanation:
The activity illustrates that phases result from the changing angles between the light source (Sun), the object (Moon), and the observer (Earth)—as the object moves around the light source, different portions of the illuminated side become visible.

Question: The mean solar day of 24 hours is primarily determined by which of Earth's motions described in the chapter?
A. Earth's revolution around the Sun
B. Earth's rotation about its own axis
C. The Moon's orbit around Earth
D. The Moon's phases cycling
Show Answer & Explanation

Answer: (B) Earth's rotation about its own axis

Explanation:
The mean solar day measures the average time between successive occasions when the Sun reaches its highest position in the sky, a cycle caused by Earth spinning once on its axis—completing one rotation in approximately 24 hours.

Question: According to the chapter's explanation, why does the Moon rise approximately 50 minutes later each successive day when observed at the same location?
A. The Moon's orbit around Earth is slowing down
B. While Earth completes a 24-hour rotation, the Moon continues moving forward in its orbit, requiring Earth to rotate slightly more for the Moon to return to the same spot
C. The Moon's distance from Earth increases daily
D. Lunar eclipses occur more frequently than realized
Show Answer & Explanation

Answer: (B) While Earth completes a 24-hour rotation, the Moon continues moving forward in its orbit, requiring Earth to rotate slightly more for the Moon to return to the same spot

Explanation:
Earth rotates in 24 hours, but during this time, the Moon also advances in its month-long orbit. Consequently, Earth must rotate an extra 50 minutes to bring an observer back to face the same Moon position, making successive moonrises occur later each day.

Question: Which statement best captures why luni-solar calendars require an intercalary month (Adhika Maasa) every 2 to 3 years?
A. The lunar year of 354 days is consistently shorter than the solar year of 365 days, and the accumulated shortfall approaches one full month
B. Leap years in the Gregorian calendar force adjustments in all other calendars
C. The Moon's phases are becoming irregular and unpredictable
D. Eclipses occur too frequently without the extra month
Show Answer & Explanation

Answer: (A) The lunar year of 354 days is consistently shorter than the solar year of 365 days, and the accumulated shortfall approaches one full month

Explanation:
Twelve lunar months total approximately 354 days, falling about 11 days short of the solar year. After roughly 3 years, this shortfall accumulates to approximately one full month, necessitating an extra intercalary month to keep lunar months aligned with seasonal cycles.

Question: How does the Indian National Calendar's year-start date of 22 March relate to Earth's position in its orbit around the Sun?
A. It marks the moment when Earth reaches its farthest point from the Sun
B. It corresponds to the spring equinox, when day and night have roughly equal length and the Sun rises exactly in the East
C. It aligns with the new Moon that occurs nearest the winter solstice
D. It indicates when the Sun reaches its highest point in the Northern Hemisphere
Show Answer & Explanation

Answer: (B) It corresponds to the spring equinox, when day and night have roughly equal length and the Sun rises exactly in the East

Explanation:
The Indian National Calendar begins on 22 March, the day after the spring equinox, when the Sun's path crossing the celestial equator results in approximately equal day and night lengths globally, marking a fundamental seasonal transition.

Question: According to the chapter's discussion of eclipses and the Moon's orbit, why do lunar and solar eclipses not occur during every full Moon and new Moon, respectively?
A. The Moon's orbit is tilted slightly relative to Earth's orbit around the Sun, so alignment occurs only at certain positions in the year
B. Eclipses are becoming rarer due to the Moon moving away from Earth
C. The Sun's brightness prevents observations of most eclipses
D. The Indian National Calendar prevents eclipse calculations from being accurate
Show Answer & Explanation

Answer: (A) The Moon's orbit is tilted slightly relative to Earth's orbit around the Sun, so alignment occurs only at certain positions in the year

Explanation:
Although full Moons and new Moons occur monthly, the Moon's orbit has a small tilt with respect to Earth's orbital plane around the Sun. Eclipses require the three bodies to align along a nearly straight line, which happens only when the Moon passes through specific positions—called nodes—favorable for eclipse formation.

Question: In the context of artificial satellites discussed in the chapter, what is meant by 'space junk' or 'space debris,' and why does it present a problem?
A. Natural meteorites that constantly bombard satellites
B. Defunct satellites and spent rocket parts that orbit Earth and can collide with operational satellites, potentially causing damage
C. The remnants of lunar rock that escaped the Moon's gravity
D. Solar radiation particles that interfere with satellite communications
Show Answer & Explanation

Answer: (B) Defunct satellites and spent rocket parts that orbit Earth and can collide with operational satellites, potentially causing damage

Explanation:
• Space debris consists of defunct satellites and rocket components left in orbit
• These objects travel at high speeds and can collide with operational satellites
• Such collisions could damage or destroy functioning satellites
• Countries are now working collaboratively to remove this hazardous debris

Question: Meghnad Saha, the chairperson of the Calendar Reform Committee, is renowned in science primarily for developing an equation that describes the relationship between which properties of matter?
A. The motion of planets in their orbits
B. Stars' temperatures and their ionization states
C. The phases of the Moon over a century
D. The tilt of Earth's rotational axis
Show Answer & Explanation

Answer: (B) Stars' temperatures and their ionization states

Explanation:
The Saha equation, a fundamental contribution to astrophysics, mathematically relates a star's temperature to the state of ionization of its atoms, enabling scientists to determine stellar properties by analyzing light spectra.

Question: The chapter states that festivals such as Makar Sankranti follow a solar sidereal calendar and move ahead by one day every 71 years. What astronomical phenomenon causes this gradual shift of festival dates within the tropical calendar year?
A. The Moon's orbit is gradually expanding away from Earth
B. A slow wobble in Earth's rotational axis, similar to a spinning top that wobbles, causes a precession of the equinoxes
C. The Sun's brightness is slowly increasing over centuries
D. Leap years are added inconsistently across different cultures
Show Answer & Explanation

Answer: (B) A slow wobble in Earth's rotational axis, similar to a spinning top that wobbles, causes a precession of the equinoxes

Explanation:
Earth's axis exhibits a slow wobble due to gravitational influences, causing a gradual shift in the orientation of the equinoxes and solstices relative to the stars—a phenomenon called precession, which makes sidereal-calendar dates drift slowly forward in the tropical year.

Question: According to Activity 11.1 and the chapter's discussion of Moon visibility, at what time of the lunar cycle is the Moon most easily observed at sunrise, and why?
A. During the new Moon phase, when the Moon is closest to the Sun
B. During the waning phase, when the Moon is moving away from the Sun and becomes visible in the western direction before sunrise
C. During the full Moon phase only
D. The Moon cannot be seen at sunrise under any circumstances
Show Answer & Explanation

Answer: (B) During the waning phase, when the Moon is moving away from the Sun and becomes visible in the western direction before sunrise

Explanation:
During the waning phase, the Moon gradually moves away from the Sun in the sky. By the time several days have passed, the Moon's position in the western direction at sunrise makes it visible before the Sun rises in the east, making this an ideal time for observation.

Question: How do festivals based on luni-solar calendars differ from those based purely on lunar calendars with respect to their occurrence dates in the Gregorian calendar year after year?
A. Luni-solar festivals stay fixed on the same Gregorian date every year
B. Luni-solar festivals shift by less than a month between years because intercalary months prevent large seasonal drift, whereas purely lunar festivals can shift by up to several months
C. Both types shift equally and unpredictably
D. Purely lunar festivals are more reliable for scheduling
Show Answer & Explanation

Answer: (B) Luni-solar festivals shift by less than a month between years because intercalary months prevent large seasonal drift, whereas purely lunar festivals can shift by up to several months

Explanation:
Luni-solar calendars add an intercalary month every few years to correct for the difference between the lunar and solar cycles, keeping festivals relatively stable within a narrow window. Purely lunar calendars lack this correction, causing festival dates to drift progressively earlier through the Gregorian year.

Question: The chapter mentions that ancient Indian texts like the Taittirīya Saṁhitā recorded observations of the Sun's apparent motion. What pattern did these observations describe that occurs annually?
A. The Moon phases repeating every 29.5 days
B. The Sun's apparent northward movement (Uttarayan) for six months and southward movement (Dakshinayan) for six months, related to changing seasons
C. The precession of stars visible at night
D. Random variations in sunrise and sunset times
Show Answer & Explanation

Answer: (B) The Sun's apparent northward movement (Uttarayan) for six months and southward movement (Dakshinayan) for six months, related to changing seasons

Explanation:
Ancient observers noted that the Sun does not rise and set at exactly the same point year-round. From December to June, it rises progressively northward of due east (Uttarayan), and from June to December, it moves southward (Dakshinayan)—a pattern tied directly to seasonal changes.

Question: In the context of the chapter's discussion of calendars and festivals, the Positional Astronomy Centre annually publishes the Rashtriya panchang. What is the primary purpose of this publication?
A. To predict when meteorites will hit Earth
B. To provide advance calculations of celestial object positions for determining festival dates uniformly across India's different geographic regions
C. To track changes in the Moon's distance from Earth
D. To record historical lunar eclipse data
Show Answer & Explanation

Answer: (B) To provide advance calculations of celestial object positions for determining festival dates uniformly across India's different geographic regions

Explanation:
The Rashtriya panchang is a detailed astronomical reference published by India's Positional Astronomy Centre to calculate precise positions of the Sun and Moon. Since Indian festival dates depend on lunar phases and exact times vary by location due to sunrise occurring earlier in the east and later in the west, this uniform reference ensures consistent festival dates nationwide.

Question: In Activity 11.1, when observing the Moon over several weeks starting after a full Moon, what sequence of changes would a student most likely record regarding the Moon's brightness and its distance from the Sun?
A. The bright portion stays constant while the Moon moves farther from the Sun each day
B. The bright portion decreases while the Moon moves closer to the Sun each day
C. The bright portion increases while the Moon moves closer to the Sun each day
D. The bright portion decreases while the Moon moves farther from the Sun each day
Show Answer & Explanation

Answer: (B) The bright portion decreases while the Moon moves closer to the Sun each day

Explanation:
As the Moon enters its waning period after the full Moon, the illuminated portion seen from Earth shrinks over approximately two weeks. Simultaneously, as shown in Activity 11.1 and section 11.1.2, the Moon appears to move progressively closer to the Sun in the sky during the waning period, since on a full Moon day the Moon is nearly opposite the Sun, and as it wanes it moves toward the Sun's direction.

Question: Based on the ball-and-stick demonstration in Activity 11.2, at which position would the observer see a crescent Moon phase?
A. When the ball is held directly opposite the lamp, with the observer facing its illuminated side completely
B. When the ball is held at a slight angle to the lamp, so less than half of the illuminated portion faces the observer
C. When the ball is held toward the direction of the lamp, with only the non-illuminated side visible to the observer
D. When the ball is held at a 90-degree angle from the lamp, with exactly half of the illuminated portion visible
Show Answer & Explanation

Answer: (B) When the ball is held at a slight angle to the lamp, so less than half of the illuminated portion faces the observer

Explanation:
The crescent phase occurs when less than half of the Moon's illuminated side is visible from Earth. In the activity, this corresponds to positions D and F, where the ball is held at an angle between the lamp and the observer, showing only a thin sliver of illumination. This happens when the Moon is between the new Moon position (E, toward the lamp) and the half-Moon positions (C and G).

Question: How does the mean solar day of 24 hours relate to observations that could be made during Activity 11.3 with the shadow stick?
A. The time when the shadow is shortest occurs at different times each day because Earth's rotation speed varies
B. The interval between times of shortest shadow on consecutive days represents one complete rotation of Earth relative to the Sun
C. The length of the shortest shadow changes in a predictable pattern that defines the 24-hour period
D. The shortest shadow always occurs at noon according to the Gregorian calendar regardless of the observer's location
Show Answer & Explanation

Answer: (B) The interval between times of shortest shadow on consecutive days represents one complete rotation of Earth relative to the Sun

Explanation:
The mean solar day of 24 hours is defined as the average time for the Sun to return from its highest position in the sky on one day to the highest position the next day. In Activity 11.3, students find when the shadow is shortest (indicating the Sun's highest point) and record this time. The difference in time between these shortest-shadow moments on consecutive days demonstrates the length of one solar day, which equals 24 hours on average.

Question: Why would a purely lunar calendar be impractical for farmers in India trying to plan when to plant crops in spring?
A. • A lunar year contains 12 lunar months totalling 354 days, which is about 11 days shorter than the solar year • Over several years, lunar calendar months drift backward through the seasons • Eventually, planting months marked in the lunar calendar occur during different seasons
B. Lunar calendars are based on inaccurate observations of the Moon's phases and cannot be trusted
C. The Moon is not visible during daylight hours, making it impossible to track time during the growing season
D. The phases of the Moon change too rapidly to provide reliable monthly divisions for agricultural planning
Show Answer & Explanation

Answer: (A) • A lunar year contains 12 lunar months totalling 354 days, which is about 11 days shorter than the solar year • Over several years, lunar calendar months drift backward through the seasons • Eventually, planting months marked in the lunar calendar occur during different seasons

Explanation:
Section 11.2.1 explicitly explains this problem: because a lunar year (354 days) is about 11 days shorter than the solar year (365 days), the seasons do not remain synchronized to the same lunar months in successive years. Over time, what was once a spring planting month in the lunar calendar would shift to winter or other seasons, making it useless for seasonal agriculture without an additional mechanism like the intercalary month used in luni-solar calendars.

Question: The chapter states that the Indian National Calendar begins on 22 March. This date is significant because it represents:
A. The day when Earth's axis is tilted most toward the Sun and daylight is longest
B. The first day of the Gregorian calendar year in India, chosen for administrative convenience
C. The day after the spring equinox, when day and night are approximately equal in length
D. The date when the Moon completes one full cycle through all its phases
Show Answer & Explanation

Answer: (C) The day after the spring equinox, when day and night are approximately equal in length

Explanation:
Section 11.2.4 specifies that the Indian National Calendar year begins on 22 March, which is the day after the spring equinox. The chapter's discussion of solar calendars and seasonal synchronization indicates that equinoxes are significant astronomical events marking when day and night are roughly equal. This start date ensures the calendar aligns with natural seasonal cycles on which agriculture and traditional observations depended.

Question: According to the chapter's discussion of festivals and calendars, Diwali and Buddha Purnima both occur on full Moon days, yet their Gregorian calendar dates shift by different amounts year to year. What explains this difference in how much their dates shift?
A. Diwali is celebrated according to a luni-solar calendar while Buddha Purnima follows a purely lunar calendar
B. Diwali occurs in a month with an intercalary addition while Buddha Purnima does not
C. Diwali is observed on the new Moon while Buddha Purnima is observed on the full Moon
D. The intercalary month in luni-solar calendars is inserted in the month of Kartika but not in Vaisakha
Show Answer & Explanation

Answer: (A) Diwali is celebrated according to a luni-solar calendar while Buddha Purnima follows a purely lunar calendar

Explanation:
Section 11.3 states that Diwali falls on the new Moon of Kartika, while Buddha Purnima falls on the full Moon of Vaisakha. The chapter explains that festivals based on luni-solar calendars have date shifts that are typically less than a month because the intercalary month is added every few years to correct for the difference between lunar and solar years. However, purely lunar calendar festivals can shift by a full month or more. Diwali, being part of a luni-solar calendar system, experiences smaller annual date shifts than festivals tied to purely lunar calendars.

Question: Vikram Sarabhai, mentioned as the founder of India's space program, lived before artificial satellites were routinely launched. How does the chapter suggest his work ultimately contributed to modern timekeeping and calendar systems?
A. His mathematical theories improved the accuracy of lunar phase calculations used in luni-solar calendars
B. His space satellites enabled the Government of India to publish the Rashtriya panchang with greater precision and distribute festival dates uniformly across the country
C. He advocated for abandoning traditional calendars in favor of the Gregorian calendar system
D. His work directly led to the creation of the Indian National Calendar in 1956
Show Answer & Explanation

Answer: (B) His space satellites enabled the Government of India to publish the Rashtriya panchang with greater precision and distribute festival dates uniformly across the country

Explanation:
Section 11.4 discusses how ISRO satellites support communication and data gathering, and section 11.3 notes that the Positional Astronomy Centre publishes the Rashtriya panchang to maintain uniformity in festival date calculations across India. While Sarabhai pioneered the Indian space program (not shown launching satellites himself in this chapter's timeline), the infrastructure he established enabled satellite-based observations and rapid dissemination of astronomical calculations that modern calendar and festival coordination now depend on. This represents an indirect but significant contribution to how India keeps and coordinates time through space technology.

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