CBSE Class 7 Science Light Assignment

L-15 LIGHT

Q.1 Fill in the blanks
a) Light travels along a ........................ line.
Answer: straight
In simple words: Light always moves in a straight line path, which is known as rectilinear propagation of light.

Exam Tip: Remember the term 'rectilinear propagation' for light traveling in a straight line.

b) An image that cannot be obtained on a screen is called a ....................... image.
Answer: virtual
In simple words: A virtual image appears to be formed behind the mirror and cannot be caught on a screen.

Exam Tip: Real images can be caught on a screen, but virtual images cannot.

c) The image formed by ................... mirror is erect, virtual and is of the same size as the object.
Answer: plane
In simple words: A plane mirror always forms an erect image of the exact same size as the object placed in front of it.

d) An image which can be obtained on a screen is called a ........................ image.
Answer: real
In simple words: An image that can be captured on a physical screen is a real image.

Exam Tip: Real images are formed by actual intersection of light rays.

e) A ................. lens can be used as a magnifying glass.
Answer: convex
In simple words: A convex lens magnifies objects when they are placed close to it.

Exam Tip: Convex lenses are thicker in the middle and converge light rays.

Q.2 Match the following
a) Lateral inversion in a plane mirror - ii) A Plane mirror
b) Reading printed matter using a lens - i) A convex lens
c) Rear-view mirror in vehicles - iv) A convex mirror
d) Dentist examining teeth - v) A concave mirror
e) Newton color disc - iii) A Newton's Disc
Answer:
(a) matches with (ii)
(b) matches with (i)
(c) matches with (iv)
(d) matches with (v)
(e) matches with (iii)
In simple words: Different optical devices are used for specific purposes based on their reflection and refraction properties.

Exam Tip: Memorize everyday applications of spherical mirrors and lenses.

Q.3 Recognize these mirrors and name them.
A)
i) Convex mirror
ii) Concave mirror
B) Recognize these lenses and name them.
i) Convex lens
ii) Concave lens
Answer:
A) (i) Convex mirror, (ii) Concave mirror
B) (i) Convex lens, (ii) Concave lens
In simple words: Mirrors and lenses are identified by whether their reflecting or refracting surfaces bulge outwards or curve inwards.

Exam Tip: Convex surfaces bulge outwards; concave surfaces cave inwards.

Q.4 Fill in the blanks.
a) A convex lens converges (Bends inwards) the light falling on it, therefore it is called a ....................................... lens.
(Diverging lens or converging)
Answer: converging
In simple words: Convex lenses bring parallel light rays together to a single focal point.

Exam Tip: Convex = Converging.

b) A concave lens diverges (Bends outwards) the light falling on it, therefore it is called a ................................... lens.
(Diverging lens or converging lens)
Answer: diverging lens
In simple words: Concave lenses spread light rays apart.

Exam Tip: Concave lens = Diverging lens.

Q.5 Here we have made a circle divided into seven segments for you. Paint or paste seven rainbow colours in these segments.
Answer:
The seven segments of the circle (Newton's disc) should be filled with the seven colors of the rainbow in order: Red, Orange, Yellow, Green, Blue, Indigo, and Violet (VIBGYOR).
In simple words: When a disc painted with all seven rainbow colors spins rapidly, it appears white due to the blending of colors.

Exam Tip: Remember the acronym VIBGYOR for the colors of the spectrum.

Q.6 Carefully observe and tick the right choice?
a)
Images of a candle in a plane mirror - Virtual image
Image formed by a convex lens - Real image (can also be virtual depending on object position, typically real in standard textbook contexts)
Image formed by a concave mirror - Real image (can also be virtual when object is very close)
Image formed by a magnifying glass (convex lens close to object) - Virtual image.
Answer:
 
In simple words: Plane mirrors always make virtual images, while convex lenses and concave mirrors typically form real images except when objects are placed very close to them.

Exam Tip: Always analyze the object distance from mirrors and lenses to determine image nature.