Q. 1. Define a prism.
Ans. Read Art. 9.04.
Q.2. Define edge of the prism.
Ans. Read Art. 9.04.
Q. 3. Define angle of prism.
Ans. Read Art. 9.04.
Q. 4. Define angle of deviation.
Ans. The angle through which aray of light turns away from its original path on pasing through a
prism, is called angle of deviation.
Q.5. On what factors does the angle of deviation depend?
Ans. The angle of deviation depends upon the following factors :
() The angle of incidence.
() The refracting angle of the prism.
(i1) The material of theprism. (Refractive Index)
(iv) The colour of the light used i.e., wavelength of light.
Q.6. What is the relation between different angles involved in refraction through aprism?
Ans. Read Art. 9.05.
Q.7. Define angle of minimumdeviation.
Ans. The least value of the angle of deviation is known as the angle of minimum deviation.
[Art. 9.06 (a)]
0.8. How isangle of minimumn deviation related withrefractive index of prism materia.
Ans. Read Art. 9.06 (b).
Q. 9. What is the speciality about minimum deviation?
Ans. Under minimum deviation condition, light ray travels inside prism parallel to the base ot
prism and the angle of incidence = angle of emergence.
Refactive.Index of Prism Material, Glass Slab and Transparent Liquid 169
Doesthe angle of minimum deviation depend upon the colour of light used?
0. 10.
it different for different
Ans. Yes, is
colours or wavelengths.
What word helps in remembering the name of seven colours into which white light is
splitted?
Ans. The
word is VIBGYOR.
A12. What name is givern to the phenomenon of splitting white light into seven colours?
light.
Ans. The phenomenon is called dispersion of
a13. What does the graph between i and D indicate?
Ans. There is only one unique value of angle of incidence for which the deviation is minimum.
there are two values of angle of incidence for one value of angle of deviation?
Q, 14. Why
Anis, If the emergent ray be reversed, then angle e becomes i and angle i becomese. The reversed ray
will have same deviation as before.
Hence, i and e are two different values for same angle of deviation.
0 15. Which colour will travel () fastest () slowest in prism?
Ans. () Red (i) Violet.
0.16.Does a beam of white light givea spectrum on passing a hollow prism?
Ans. No. Because dispersion does not occurs in ai.
Q. 17. Which colour deviates ) most (ii) least?
Ans. ()Violet (ii) Red.
Q. 18. Will allcolours of light travel with samne speed inside a prism?
Ans. No. Red colour travels fastest and violet colour travels slowest.
Q. 19. Which colours have hightest and smallest refractive index? Why?
Ans. Refractive index is smalest for red colour and highest for violet colour.
1
Refractive Index o«
wavelength
Q20. What is Cauchy's relation?
Ans. It is the relation between refractive index of a transparent medium and colour of light.
B C
n =A +
Q 21. Can X-rays be dispersed?
Ans. Yes.
Q 22. what is angular deviation?
8. lhe angle between the emergent rays of any two colours is called angular deviation of those
colours.
23. On what factors does angular deviation depend?
Ans. (i) Angle of prism (i) refractive index.
Q24. What is dispersive; power of prism?
Ans, It is defned as the ratioof the angular deviation for the two colours to the mean deviation
produced by the prism.
Q25.
What is the factor on which dispersive power depends?
as. It depends upon refractive index of the material of prism.
