Question

You are observing a 20 cm-tall object in a pinhole camera with a screen at the end. The screen is 25 cm from the pinhole. The image on the screen is 5 cm tall.

(1) What can you say about the image?

a. Upright, Reduced
b. Inverted, Enlarged
c. Inverted, Reduced
d. Upright, Enlarged

Answer 1

The image produced by a pinhole camera when observing a 20 cm-tall object is inverted and reduced in size, specifically 5 cm tall when the screen is 25 cm away from the pinhole.

Step-by-step explanation:

When you are observing a 20 cm-tall object in a pinhole camera with a screen 25 cm from the pinhole and the image on the screen is 5 cm tall, you can determine that the image has specific characteristics. In a pinhole camera, the image is always inverted and is the same orientation as with lenses or mirrors. Given that the image is 5 cm tall while the object is 20 cm tall, the image is also reduced in size. Therefore, the correct answer to the question is:

c. Inverted, Reduced

Answer 2

Upright, Reduced

Step-by-step explanation:

Given that,

Height of the object, h = 20 cm

Image distance, v = 25 cm

Height of the image, h' = 5 cm

We know that the magnification of the mirror is given by :

`m=(h')/(h)=(v)/(u)`

`(5)/(20)=(25)/(u)`

u = -100 cm (negative due to sign conventions)

Let f is the focal length of the lens. It can be calculated as :

`(1)/(f)=(1)/(v)-(1)/(u)`

`(1)/(f)=(1)/(25)-(1)/((-100))`

f = 20 cm

It is seen that the focal length of the lens is positive. So, it is a convex lens. The image formed by the convex lens is Upright, Reduced. Hence, the correct option is (a).