PHYSICS NOTES - PINHOLE CAMERA - Q2 - Q3

 Q.2 (a) What is principle of pinhole camera?

(b) Briefly describe the construction and working of a pinhole camera. Draw a diagram in support of your answer.

Ans. (a) Principle of Pinhole Camera:

It is based on the principle that light travels in straight lines i.e. Rectilinear Propagation of Light.

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Ans. (b) Construction of Pinhole Camera:

• It consists of a rectangular cardboard box, such that one is made out of ground glass screen.

• The side opposite to the ground glass screen has a hole in the middle, whose size is equal to the pinhead of a common pin.

• The box is blackened from inside so as to absorb any light which falls on its walls directly or indirectly.

Working of Pinhole Camera:

• Consider a candle AB in front of the pinhole camera.

• The rays starting from different points of candle, travel in all directions.

• A ray of light starting from point A along AH, after passing through pinhole falls on the ground glass screen at point A1.

• Similarly, another ray starting from point B along BH after passing through pinhole falls on the ground glass screen at point B1.

• Thus, all the rays starting between A and B after passing through pinhole will meet the screen between points A1 and B1.

• Thus,A1 and B1 is the image of object AB.

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Q.3 (a) State three characteristics of the image formed by pinhole camera.

Ans: Characteristics of the image formed by pinhole camera:

• It is real i.e., formed on screen

• It is inverted

• It is generally smaller than the size of the object

(b) How is the image formed in the camera is affected when,
(i) the distance of the screen from the pinhole increases.

Ans: If the distance between the screen and pinhole increases, the size of image will increase.

(ii) if the distance of the object from pinhole increases.

Ans: If the distance of the object from pinhole increases, the size of image will decrease.