Light
1). Fill in the blanks:
(a) An image that cannot be obtained on a screen is called virtual image.
(b) Image formed by a convex mirror is always virtual and smaller in size.
(c) An image formed by a plane mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a real image.
(e) An image formed by a concave lens cannot be obtained on a screen.
2). Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)
Ans: F
(b) A concave lens always form a virtual image. (T/F)
Ans: T
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)
Ans: T
(d) A real image cannot be obtained on a screen. (T/F)
Ans: F
(e) A concave mirror always form a real image. (T/F)
Ans: F
3). Match the items given in Column I with one or more items of Column II.
Column I Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Column II
(a) A plane mirror              (i) Used as a magnifying glass.
(b) A convex mirror            (ii) Can form image of objects
                                              spread over a large area.
(c) A convex lens                (iii) Used by dentists to see
enlarged image of teeth.
(d) A concave mirror          (iv) The image is always inverted
and magnified.
(e) A concave lens              (v) The image is erect and of the
                                                 same size as the object.
                     (vi) The image is erect and smaller in size than the                         object.
Answer:
(a) A plane mirror →   the image is erect and of the same size as the object.
(b) A convex mirror → Can form image of objects spread over a large area.
(c) A convex lens →     Used as a magnifying glass.
(d) A concave mirror → Used by dentists to see enlarged image of teeth.
(e) A concave lens →   The image is erect and smaller in size than the object.
4). State the characteristics of the image formed by a plane mirror.
Ans: Characteristics of the image formed by a plane mirror is as follows.
(i) An image formed by a plane mirror is erect and of the same size as the object.
(ii) The image formed is at the same distance behind the mirror as the object is in front of it.
(iii) In an image formed by a mirror, the left side of the objects is seen on the right side in the image and right side of the object appears to be on the left side in the image.
(iv) The image formed is virtual.
5). Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.
Ans: A, H, I, M, O, T, U, V, W, X, Y.
6). What is a virtual image? Give one situation where a virtual image is formed.
Ans: The image formed by a plane mirror could not be obtained on a screen. Such an image is called virtual image. Image formed by a plane mirror is always virtual image.
7). State two differences between a convex and a concave lens.
| Convex lens | Concave lens |
| 1. Lenses that feel thicker in the middle than at the edges are convex lenses. | 1. Lenses that feel thinner in the middle than at the edges are concave lenses. |
| 2. a convex lens converges the light falling on it. | 2. A concave lens diverges the light falling on it. |
| 3. Image formed by a concave lens is virtual, erect and larger than the object. | 3. Image formed by a concave lens is always virtual, erect and smaller than the object. |
8). Give one use each of a concave and a convex mirror.
Ans: Concave mirrors are used in magnifying glass. Convex mirror is used in the side view mirrors of vehicles.
9). Which type of mirror can form a real image?
A concave mirror can form a real image.
10). Which type of lens forms always a virtual image?
Ans: A concave lens.
Choose the correct option in questions 11–13
11). A virtual image larger than the object can be produced by a
(i) concave lens                               (ii) concave mirror
(iii) convex mirror                            (iv) plane mirror
Ans: concave mirror
12). David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be
(i) 3 m                                                          (ii) 5 m
(iii) 6 m                                                        (iv) 8 m
Ans: 6 m
13). The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be
(i) 1 m/s                                                (ii) 2 m/s
(iii) 4 m/s                                              (iv) 8 m/s
Ans: 4 m/s
Additional Questions.
Fill in the blanks
i). The surface of water can also act like a mirror and change the path of light.
ii). Mirror changes the direction of light that falls on it.
iii). An image formed by a plane mirror is erect and of the same size as the object.
iv). convex mirror is used as side view mirror.
v). The path of light is always a straight line.
Answer the following questions.
i). What is a reflection of light?
Ans: Mirror changes the direction of light that falls on it. This change of direction is called as reflection of light.
ii). What is rectilinear propagation of light?
Ans: The light travels in a straight line, this property is called rectilinear propagation of light.
iii). How many colours are present in a rainbow?
Ans: There are seven different colours in a rainbow.
iv). What is a rainbow?
Ans: A rainbow is a large arc in the sky with many colours.
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