06: Spectrum Of Light : Icse-x-physics

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ICSE-X-Physics

06: Spectrum of Light

with Solutions - page 2

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#11
Ans : 11

#11-a
If a monochromatic beam of light undergoes minimum deviation through an equiangular prism, how does the beam pass through the prism, with respect to its base?
Ans : If a monochromatic beam of light undergoes minimum deviation through an equi-angular prism, then the beam passes parallel to the base of prism.

#11-b
If white light is used in same way as in part
(a) above, what change is expected in the emergent beam?
Ans : White light splits into its constituent colours i.e., spectrum is formed.

#11-c
what conclusion do you draw about the nature of white light in part
(b)?
Ans : We conclude that white light is polychromatic.

Qstn #12
What do you understand by the term spectrum?
Ans : 12 The colour band obtained on a screen on passing white light through a prism is called the spectrum.

Qstn #13
A ray of white light is passed through a glass prism and spectrum is obtained on a screen.
Ans : 13

#13-a
Name the seven colours of the spectrum in order.
Ans : Violet, Indigo, Blue, Green, Yellow, Orange, Red.

#13-b
Dow the colours have the same width in the spectrum?
Ans : No, different colours have different widths in the spectrum.

#13-c
which of the colour of the spectrum of white light deviates (i) the most, (ii) the least?
Ans : (i) Violet colour is deviated the most. (ii) Red colour is deviated the least.

Qstn #14
The wavelengths for the light of red and blue colours are roughly 7.8 x 10^-7
m and 4.8 x 10^-7
m respectively.
Ans : 14

#14-a
Which colour has the greater speed in vacuum?
Ans : In vacuum, both have the same speeds.

#14-b
Which colour has the greater speed in vacuum?
Ans : In glass, red light has a greater speed.

Qstn #15
(i) Draw a diagram to show the splitting of white light by a prism into its constituent colour. (ii) Draw another diagram to show how the colours of spectrum of white light can be combined to give the effect of white light.
Ans : 15 Color of light is related to its wavelength.

Qstn #16
Complete the ray diagram given below to show the nature of light produced on the screen.

Ans : 16

Qstn #17
Name the subjective property of light related to its wavelength.
Ans : 17 (i) For blue light, approximate wavelength = 4800 Å
(ii) For red light, approximate wavelength = 8000 Å