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Question 17N.2.HL.TZ0.6b.ii

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Date November 2017 Marks available [Maximum mark: 3] Reference code 17N.2.HL.TZ0.6b.ii
Level HL Paper 2 Time zone TZ0
Command term Determine Question number b.ii Adapted from N/A
b.ii.
[Maximum mark: 3]
17N.2.HL.TZ0.6b.ii

The double slit is replaced by a diffraction grating that has 600 lines per millimetre. The resulting pattern on the screen is shown.

(b.ii)

The yellow light is made from two very similar wavelengths that produce two lines in the spectrum of sodium. The wavelengths are 588.995 nm and 589.592 nm. These two lines can just be resolved in the second-order spectrum of this diffraction grating. Determine the beam width of the light incident on the diffraction grating.

[3]

Markscheme

Δλ = 589.592 – 588.995

OR

Δλ = 0.597 «nm»

N = « λ m Δ λ =»  589 2 × 0.597 «493»

beam width = « 493 600 =» 8.2 x 10–4 «m» or 0.82 «mm»

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