LIGHT QUIZ

1 ) Which Colour has the longest wavelength?

• A ) Violet

• B ) Red

• C ) Blue

• D ) Green

2 ) An object is placed 20 cm in front of a plane mirror. The mirror is moved 2 cm towards the object. The distance between the positions of the original and final images seen in the mirror is:

• a) 02 cm

• b) 22 cm

• c) 04 cm

• d) 18 cm

3) A ray of light that strikes a plane mirror PQ at an angle of incidence of 30 degree, is reflected from the plane mirror and then strikes a second plane mirror QR placed at right angles to the first mirror. The angle of reflection at the second mirror is:

• a)      90 degree 
      

• b)     30 degree

• c)     180 degree

• d)       60 degree

4) An object is placed at 100 mm in front of a concave mirror which produces an upright image (erect image). The radius of curvature of the mirror is:

• a ) less than 100 mm

• b) between 100 mm and 200 mm

• c) exactly 200 mm

• d) more than 200 mm

5) A concave mirror produces a magnification of +4. The object is placed:

• a ) at the focus

• b) Between focus and centre of curvature

• (c) Between focus and pole

• d) Beyond the centre of curvature

6. Two big mirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he finds that the size of his face in mirror A goes on increasing but that in mirror B remains the same:

• a) Mirror A is concave and mirror B is convex

• (b) Mirror A is plane and mirror B is concave

• (c) Mirror A is concave and mirror B is plane

• (d) Mirror A is convex and mirror B is concave

7. A lens of focal length 12 cm forms an erect image, three times the size of the object. The distance between the object and image is:

• (a) 8 cm

• (b) 16 cm

• (c) 24 cm

• (d) 36 cm

8) A student does the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. He can get a correct measure of the angle of incidence and the angle of emergence by following the labelling indicated in figure:

• a) A

• b) B

• c) C

• d) D

9) Power of the lens is -40, its focal length is:

• a) 4 m

• b) - 40 m

• c) - 0.25 m

• d) -25 m

10) The refractive index of glass with respect to air is 3/2 and refractive index of water with respect to air is 4/3. What will be the refractive index of water with respect to glass?

• a) 12 / 6

• b) 8 / 9

• c) 9 / 8

• d) 6 / 12