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Question 18M.2.HL.TZ1.a.i

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Date May 2018 Marks available [Maximum mark: 3] Reference code 18M.2.HL.TZ1.a.i
Level HL Paper 2 Time zone TZ1
Command term Explain Question number a.i Adapted from N/A
a.i.
[Maximum mark: 3]
18M.2.HL.TZ1.a.i

A beam of coherent monochromatic light from a distant galaxy is used in an optics experiment on Earth.

The beam is incident normally on a double slit. The distance between the slits is 0.300 mm. A screen is at a distance D from the slits. The diffraction angle θ is labelled.

M18/4/PHYSI/SP2/ENG/TZ1/03.a

A series of dark and bright fringes appears on the screen. Explain how a dark fringe is formed.

[3]

Markscheme

superposition of light from each slit / interference of light from both slits

with path/phase difference of any half-odd multiple of wavelength/any odd multiple of π  (in words or symbols)

producing destructive interference

 

Ignore any reference to crests and troughs.

[3 marks]

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