Choose the correct alternatives and rewrite the complete sentences
*1. The phenomenon of splitting of light into its component colours is
..................... .
(a) reflection (b) refraction (c) dispersion (d) rectilinear propagation
*2. Very fine particles mainly scatter ..................... light.
(a) red (b) green (c) blue (d) yellow
*3. The phenomenon of change in the ..................... of light when it passes from one transparent medium to another is refraction.
(a) Wavelength (b) frequency (c) direction (d) amplitude
*4. The refractive index depends upon the ..................... of propagation of light in different media.
(a) relative speed (b) density of medium (c) amplitude (d) frequency
5. The ratio sin i / sin r = constant is called as ..................... .
(a) dispersion (b) spectrum (c) refractive index (d) proportionality constant
6. The apparent random wavering of hot air above the heated roads causes a phenomenon called as ..................... .
(a) looming (b) mirage (c) spectrum (d) dispersion
7. The refractive index of water is ..................... .
(a) 1.33 (b) 1.31 (c) 1.36 (d) 1
8. The refractive index of ..................... is the highest.
(a) alcohol (b) flint glass (c) diamond (d) canada balsam
9. When a ray of light travels from an optically denser medium to an optically rarer medium, the ray bends ..................... .
(a) towards the normal (b) away from the normal
(c) straight (d) backwards
10. After dispersion ..................... colour deviates the most.
(a) red (b) green (c) yellow (d) violet
11. When white light is dispersed into seven colours ..................... colour bends least.
(a) blue (b) violet (c) red (d) yellow
12. ..................... light is scattered the least by the atmosphere.
(a) Red (b) Violet (c) Yellow (d) Green
13. ..................... was the first scientist to use a glass prism to obtain the spectrum of sunlight.
(a) Oersted (b) Joule (c) Newton (d) Faraday
14. The apparent depth of an object placed in a denser medium and seen through a rarer medium is ..................... .
(a) half its real depth (b) equal to the red depth
(c) less than real depth (d) greater than real depth
15. A prism is a transparent medium bound by ..................... plane surfaces inclined at an angle.
(a) two (b) three (c) four (d) one
16. When a ray of light passes from rarer medium to a denser medium, the angle of refraction is ..................... .
(a) equal to angle of incidence
(b) independent of angle of incidence
(c) smaller than angle of incidence
(d) greater than angle of incidence
17. The apparent position of a star in the sky is ..................... .
(a) slightly lower than its actual position
(b) slightly higher than its actual position
(c) same as that of its actual position
(d) far away from its actual position
18. Advanced sunlight and delayed sunset increases duration of day by
..................... minutes.
(a) 30 (b) 4 (c) 1 (d) 10
19. Amongst the following ..................... has the highest refractive index.
(a) air (b) ice (c) water (d) alcohol
20. When a ray is incident normal to the interface between any two transparent medium, the angle of incidence is ..................... .
(a) greater than angle of refraction (b)zero (c) less than angle of refraction (d) 45ยบ
21. The stars are ..................... sources of light as they are very far away.
(a) point (b) infinite (c) important (d) primary
22. Twinkling of stars is due to change in ..................... of atmosphere
(a) temperature (b) refractive index (c) pressure (d) climate
23. ..................... won a nobel prize for his outstanding work on scattering of light.
(a) Newton (b) Joule (c) Dr. C. V. Raman (d) Ohm
A. Answers.
1. Dispersion
2. Blue
3. Direction
4. Relative speed
5. Refractive index
6. Mirage
7. 1.36
8. Diamond
9. Away from the normal
10. Violet
11. Red
12. Red
13. Newton
14. Less than real depth
15. Two
16. Smaller than angle of incidence
17. Slightly higher than its actual position
18. 4
19. Alcohol
20. Greater than angle of refraction
21. Point
22. Refraction index
23. Dr. C.V. Raman. 