waec model questions vol1 2019 physics

Objective Question 16

Question 16 WAEC_MODEL_QUESTIONS_VOL1 • 2019
A converging lens is used to form a sharp image of a candle on a screen. The distance between the candle and the screen is 120 cm. When the lens is placed at one position, a sharp image is obtained. If the lens is moved 20 cm towards the screen, a sharp image is again obtained on the same screen. What is the focal length of the lens (in cm, to one decimal place)?
Answer Options
Correct Answer A. 29.2 cm
B. 24.5 cm
C. 20.0 cm
D. 33.1 cm
Correct Answer
A

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