CBSE Class 7 Science Chapter 11 Light Shadows And Reflections MCQs Set 03

Answer: (C) A lighted candle

Explanation:
The chapter defines luminous objects as those that emit their own light. A lighted candle produces light through combustion, making it luminous. The Moon reflects sunlight but does not emit its own light, a polished steel plate only reflects light, and glass is transparent but does not produce light.

Answer: (B) Light travels in straight lines only

Explanation:
The activity demonstrates that light cannot follow a curved path through a bent pipe. When the pipe was straight, the flame was visible, but bending the pipe blocked the light path. This shows that light travels only in straight lines, not around curves.

Answer: (C) Glass

Explanation:
The chapter states that transparent materials like glass allow light to pass almost completely through them. Thick cloth, cardboard, and steel plates either block light completely or allow only partial transmission.

Answer: (D) A colored object

Explanation:
Section 11.4 explains that shadows require three components: a light source, an opaque object, and a screen. The chapter explicitly states that changing the color of an opaque object does not change the color of its shadow, meaning color is not a requirement for shadow formation.

Answer: (B) The shadow becomes larger

Explanation:
When an opaque object moves closer to a light source, the angle of light rays spreading around the object increases, causing a larger shadow on the distant screen. This is evident from Activity 11.4 and the physics of light traveling in straight lines.

Answer: (B) Your right arm

Explanation:
• Light rays from your left side hit the mirror and reflect back from what appears to be the right side of the mirror
• This creates lateral inversion, the perceived left-right reversal mentioned in section 11.6
• The chapter confirms this with the example of left appearing right and right appearing left in a mirror image

Answer: (B) Pinhole camera images are inverted while mirror images are erect

Explanation:
Section 11.7 describes that a pinhole camera forms an inverted (upside down) image on a screen. In contrast, Activity 11.7 shows that a plane mirror forms an erect (upright) image. Additionally, the Dive Deeper section explicitly compares these two phenomena.

Answer: (B) Two mirrors; reflection of light from both mirrors

Explanation:
The chapter states that a periscope is made by placing two plane mirrors in a Z-shaped arrangement. The reflection from these two mirrors enables viewing of objects that are not directly visible, such as objects above a bunker or behind taller people.

Answer: (C) Due to lateral inversion in rear-view mirrors of vehicles ahead, it reads correctly

Explanation:
The chapter illustrates in section 11.6 that when viewed through a rear-view mirror of a vehicle ahead, the reversed 'AMBULANCE' text appears correct due to lateral inversion. This helps drivers ahead recognize the ambulance approaching.

Answer: (C) It was upside down (inverted)

Explanation:
Activity 11.9 specifically notes that the image of the candle flame formed on the screen is upside down, that is, inverted. This is a distinctive and surprising characteristic of pinhole camera images, in contrast to plane mirror images which remain upright.

Answer: (B) Transparent materials allow almost complete light passage while translucent allow only partial passage

Explanation:
Section 11.3 and Activity 11.3 clearly distinguish between these materials: light passes almost completely through transparent materials like glass, while it passes only partially through translucent materials like tracing paper. This allows us to see clearly through glass but only dimly through tracing paper.

Answer: (B) The three mirrors creating multiple images through repeated reflections

Explanation:
The chapter explains that a kaleidoscope uses three mirrors arranged in a triangle, and due to reflections of reflections, many interesting patterns are formed. Since there are three mirrors and multiple images result from their reflections, different patterns appear each time the kaleidoscope is rotated and the arrangement of beads changes relative to the mirrors.

Answer: (B) How much light passes through it

Explanation:
Section 11.3 classifies materials based on light transmission: opaque materials block light completely, translucent materials allow partial passage, and transparent materials allow almost complete passage. This classification depends entirely on the proportion of light that can pass through the material.

Answer: (B) Light pollution, reduced forest cover, and excessive tourism

Explanation:
The chapter's introduction explicitly states that the number of fireflies is decreasing due to three specific factors: light pollution, reduced forest cover, and excessive tourism in the region.

Answer: (B) Light travels in straight lines and changes direction when it strikes a mirror

Explanation:
• Activity 11.6 shows that as the mirror was tilted, the light spot moved on the wall
• The light always travels in straight lines but changes direction upon hitting the mirror
• This directly demonstrates that mirrors reflect light, changing its path while maintaining the straight-line property of light travel

Answer: (B) Metal surface mirror making

Explanation:
Section 11.6's Fascinating Facts box specifically mentions that while glass mirrors became common and metal mirror-making declined, the tradition of making Aranmula Kannadi—a unique metal surface mirror—has survived in Kerala for centuries, representing a preservation of ancient mirror-making craftsmanship.

Answer: (B) The light spot disappeared from the screen

Explanation:
Activity 11.1 states that when all three holes were not in the same line, the light spot could not be obtained on the screen. This observation directly supports the conclusion that light travels only in straight lines, and any break in the linear alignment blocks the light path.

Answer: (B) Light travels in straight lines and cannot bend around corners

Explanation:
The chapter establishes through multiple activities that light travels only in straight lines. Since light cannot curve or bend around obstacles naturally, it cannot travel around a corner to reach your eyes unless reflected by a surface (which would require a mirror or similar reflective object).

Answer: (B) Flat cut-out figures are placed between a light source and a screen

Explanation:
The Fascinating Facts box in section 11.4 explains that in shadow puppetry, flat cut-out figures called shadow puppets are placed between a light source and a screen. By moving the puppets and the light, puppeteers create life-like movements, which is exactly how shadows and light interaction work.

Answer: (B) Light reflected from the Sun

Explanation:
Section 11.1 explicitly defines the Moon as a non-luminous object and states that it does not emit its own light but instead reflects the light emitted by the Sun that falls on it. This reflected sunlight is what makes the Moon visible during nighttime.

Answer: (C) All three: a light source, an opaque object, and a screen

Explanation:
Section 11.4 and Activity 11.4 establish that three essential components are required: a source of light to produce light rays, an opaque object to block the light, and a screen or surface for the shadow to appear on. Without any one of these, a shadow cannot form or be observed.

Answer: (B) It is translucent and allows light through while diffusing it to show an image

Explanation:
Tracing paper is translucent, meaning it allows light to pass through partially. This property makes it ideal for viewing the inverted image formed by the pinhole camera. Unlike transparent materials, it scatters light enough to make the image visible, but unlike opaque materials, it allows light passage to form the image.

Answer: (B) Your right cheek

Explanation:
Lateral inversion causes left and right to appear reversed in a mirror image. If the image appears to touch its left cheek, it is actually touching your right cheek because the mirror reverses the left-right orientation. The chapter illustrates this principle with the example of raising the left arm, which appears as the right arm in the image.

Answer: (B) It allows viewing of objects above or below the observer's line of sight without direct visibility

Explanation:
A periscope uses two plane mirrors in a Z-shaped arrangement such that light from a distant object reflects off the first mirror, then the second mirror, allowing the observer to see objects that are not directly visible. This design is used in submarines, tanks, and by soldiers to see outside bunkers without exposing themselves.

Answer: (B) The milk particles scatter the light, making the straight path visible

Explanation:
The Dive Deeper section in 11.3 mentions that milk is added to water to make the laser beam easily visible. The milk particles scatter the light beam, making the normally invisible light path visible as a straight line through the water, thereby demonstrating that light travels in a straight line even in transparent media.