Question

State the effect on the image formed by a pinhole camera if the object is moved towards the pinhole.
A. Its size increases
B. Its size decreases
C. Its size remains the same
D. A pinhole camera can never form images

Answer 1

Hint: First understand what a pinhole camera is. Then understand how a pinhole camera works and how the image is formed on the screen and check what change will be observed on the image, when the distance between object and pinhole is reduced.

Complete answer:
Given an object is moved towards a pinhole, and we have to answer about the size of the image formed.First let us know what a pinhole camera is. A pinhole camera is a simple camera without any lens, it is in the shape of a box, a tiny hole is made on one side of the box and the image is formed on the opposite side of the hole.
Let us know how an image is formed in a pinhole camera. The working principle of pinhole cameras is rectilinear propagation of light. The aperture or the hole is very small (close to a diameter of ) that is only one ray from each point of the object can pass through the pinhole and falls on the screen or the opposite side of the hole, which means there is one-to-one correspondence between the points on the objects and the points of the image formed on the screen.
So, if the distance between the object and the pinhole is reduced, the image formed will be smaller and brighter. Therefore, if the object is moved towards the pinhole, the size of the image formed will be decreased.

Hence, the correct option is B.

Note:By rectilinear propagation of light, we mean light always travels in a straight line. An important point to remember is that the image formed in a pinhole camera is inverted. The function of a pinhole camera and our human eye is quite similar, in the human eye too light enters our eye and forms an inverted image on the retina then the information is sent to the brain, the image is flipped and we see a right side up image.