IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

# To know the working of Pin Hole Camera

## Introduction

Just let the light from an object go through a small hole in a card and on the other side you can pick up a real image on a screen. Make the simple pin hole camera and see which objects can be imaged and which cannot.

## Apparatus

The camera we make is a PVC pipe piece of few cm length. At one end we fix a paper with a small hole of about one mm of diameter and at the other end we fix a slightly oily butter paper.

## Procedure

1. Put up two LEDs, one blue and one red, side by side. Connect them to adapters and lit them.
2. Face your camera towards the LEDs, the hole towards the LEDs. Can you see the image?
3. Check, which of the image is on left and which is on right. Is it in the same order as the actual LEDs or it gets reversed in order?
4. Check if you can see the details of an LED in the image, its round body and so on.
5. Increase the distance of the camera from the LEDs. What happens to the image?
6. Face the camera towards other objects like a photo on your mobile screen. Are you able to see the image?

## Discussion

An image is formed when at any point on the screen, you get light coming from a definite point of the object. In a lens, refraction ensures that. In pin hole the small size of the hole ensures that. The image is faint as only a small pencil of light from a given point of object reaches the screen.