Page 220 - Physics Coursebook 2015 (A level)

Cambridge International AS Level Physics
7 A hydrogen discharge lamp produces a spectral line of wavelength 656 nm. Calculate the angles
at which a diffraction grating, with 5000 lines cm−1, would produce the first and second maxima for
this light. [5]
8 a Explain what is meant by the term superposition. [2] b In a Young double-slit experiment using yellow light of wavelength 590 nm from a sodium
discharge tube, a student sets up a screen 1.8 m from the double slit. He measures the distance
between 12 fringes as 16.8 mm. Calculate the separation of the slits. [3] c State the effect of:
i using slits of narrower width (but the same separation) [2]
ii using slits with a smaller separation but of the same width [2]
9 a A laser light is described as producing light which is both highly coherent and highly monochromatic.
Explain what is meant by the terms coherent and monochromatic. [2]
b Figure 14.30 shows the setup used to analyse the spectrum of a sodium discharge lamp using a diffraction grating with 5000 lines cm−1. Figure 14.31 shows the spectral lines observed in the developed photographic film.
collimator
diffraction grating
sodium lamp
θ
B
A
photographic film
Figure 14.30 Experimental setup for End-of-chapter Question 9.
violet blue green yellow red violet blue green yellow red
AB
Figure 14.31 Spectral lines produced.
i Explain why two spectra are observed. [2]
ii Study the two spectra and describe two differences between them. [2]
iii ThegreenmaximumnearendAisatanangleθof19.5°.Calculatethewavelengthofthegreenlight. [3] iv Calculatetheangleproducedbythesecondgreenline. [2]
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