DP Physics (first assessment 2025)

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Question 22N.1A.SL.TZ0.14

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Date November 2022 Marks available [Maximum mark: 1] Reference code 22N.1A.SL.TZ0.14
Level SL Paper 1A Time zone TZ0
Command term Question number 14 Adapted from N/A
14.
[Maximum mark: 1]
22N.1A.SL.TZ0.14

A ray of light enters from air into a water droplet of radius r at point S. S is a vertical distance h from the centre of the droplet. The droplet has a refractive index n and the angle of refraction is θ.

What is sin θ?


A.  nhr

B.  rnh

C.  hnr

D.  nrh

[1]

Markscheme

C

Examiners report

This question can be answered using Snell's law and geometry, but a much more efficient way is by exaggerating the variables. Suppose that the value of n increases. This must lead to a smaller value of θ (the refracted ray will be closer to the normal), hence sin θ must decrease when n increases (alternatives A and D eliminated). Now suppose that the vertical distance h decreases to zero, in this case sin θ should also be zero (alternative B eliminated, only C remains).

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