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Question 19M.3.HL.TZ1.7b.ii

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.3.HL.TZ1.7b.ii
Level HL Paper 3 Time zone TZ1
Command term Explain, State Question number b.ii Adapted from N/A
b.ii.
[Maximum mark: 2]
19M.3.HL.TZ1.7b.ii

A box is in free fall in a uniform gravitational field. Observer X is at rest inside the box. Observer Y is at rest relative to the gravitational field. A light source inside the box emits a light ray that is initially parallel to the floor of the box according to both observers.

(b.ii)

State and explain the path of the light ray according to observer Y.

[2]

Markscheme

ALTERNATIVE 1
light must hit right wall of box at same place as determined by X ✔

«but box is accelerating» so path must be curved downward ✔

ALTERNATIVE 2
light is affected by gravity «for the observer at rest to the ground» ✔

so the path is curved downward/toward the ground ✔

Examiners report

Quite a high number of candidates, in b ii), stated incorrectly, that the light ray will be curved upward.

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