# physics questions light

1. What is the wavelength of ultraviolet rays of 3.0 x 1015 Hz frequency?

100 nm

200nm

300nm

400nm

2. A ray of light is incident on a plane mirror at an angle of 40o with the mirror surface. What will be the angle of reflection?

40

50

90

150

3. What is the speed of light in carbon disulphide if its refractive index is 1.628?

1.37 x 108 m/s

1.84 x 108 m/s

3.00 x 108 m/s

4.88 x 108 m/s

4. What is the speed of light in carbon disulphide if its refractive index is 1.628?

• 1.37 x 108 m/s
• 1.84 x 108 m/s
• 3.00 x 108 m/s
• 4.88 x 108 m/s

5. Which of the following conditions is not necessary to observe an interference pattern between two sets of waves?

The waves must have the same wavelength.

The waves must have a constant phase difference.

The waves must have the same amplitude.

The waves must have the same frequency.

6. A concave spherical mirror has a radius of curvature 15 cm. A 1 cm tall bulb is placed in front of the mirror such that its image is formed 10 cm in front of the mirror. If you measure distance from the optic center of the mirror,
(A) What is the focal length of the mirror?
(B) What is the position of the object?
(C) What is the magnification of the image?
(D) What is the height of the image?

7. Where should the birthday candle of height 5 cm be placed in front of a convex lens of focal length 15 cm so that a real image will be formed at a distance of 25 cm from the lens? What is the height of this image?

8. Explain how a mirage is formed.

9. How many lines/cm should be present in a diffraction grating to produce the first bright fringe at an angle of 4o when yellow light of wavelength 580 nm passes through it?

10. Explain the working of a laser.

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