Test Index

JAMB Physics 2017 Paper

© africaexams.com

Question : 16

Total: 49

Calculate the height of the image formed by a pinhole camera of length 12cm used to photograph an object 60cm away from the hole and 70cm high

10 cm
16 cm
5 cm
14 cm

Solution:

Concept:

A pinhole camera forms an image by similar triangles, so magnification equals the ratio of camera length to object distance.

Explanation:

Magnification,

m = \dfrac{\text{camera length}}{\text{object distance}}

m = \dfrac{12\text{ cm}}{60\text{ cm}} = 0.2

Also,

m = \dfrac{\text{image height}}{\text{object height}}

So, image height

= m \times \text{object height}

Image height

= 0.2 \times 70\text{ cm}

Image height

= 14\text{ cm}

Answer:

D. 14 cm

© africaexams.com

Go to Question:

Prev Question

Next Question