DP Physics (last assessment 2024)

Test builder »

Question 19N.2.HL.TZ0.b(ii)

Select a Test
Date November 2019 Marks available [Maximum mark: 2] Reference code 19N.2.HL.TZ0.b(ii)
Level HL Paper 2 Time zone TZ0
Command term Calculate Question number b(ii) Adapted from N/A
b(ii).
[Maximum mark: 2]
19N.2.HL.TZ0.b(ii)

The lens of an optical system is coated with a thin film of magnesium fluoride of thickness d. Monochromatic light of wavelength 656 nm in air is incident on the lens. The angle of incidence is θ. Two reflected rays, X and Y, are shown.

The following refractive indices are available.

Air                            = 1.00
Magnesium fluoride = 1.38
Lens                         = 1.58

The thickness of the magnesium fluoride film is d. For the case of normal incidence (θ = 0),

calculate the smallest value of d that will result in destructive interference between ray X and ray Y.

[2]

Markscheme

2dn=λ2 ✔

d=«λ4n=6564×1.38=» 119 «nm» ✔

 

NOTE: Award [2] for bald correct answer

Syllabus sections