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Question 18N.2.HL.TZ0.5b.iii

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Date November 2018 Marks available [Maximum mark: 3] Reference code 18N.2.HL.TZ0.5b.iii
Level HL Paper 2 Time zone TZ0
Command term Outline Question number b.iii Adapted from N/A
b.iii.
[Maximum mark: 3]
18N.2.HL.TZ0.5b.iii

A low-pressure hydrogen discharge lamp contains a small amount of deuterium gas in addition to the hydrogen gas. The deuterium spectrum contains a red line with a wavelength very close to that of the hydrogen red line. The wavelengths for the principal lines in the visible spectra of deuterium and hydrogen are given in the table.

Light from the discharge lamp is normally incident on a diffraction grating.

(b.iii)

The light source is changed so that white light is incident on the diffraction grating. Outline the appearance of the diffraction pattern formed with white light.

[3]

Markscheme

centre of pattern is white ✔

coloured fringes are formed ✔

blue/violet edge of order is closer to centre of pattern

OR

red edge of order is furthest from centre of pattern ✔

the greater the order the wider the pattern ✔

there are gaps between «first and second order» spectra ✔

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