Q19 of 284 Page 252

When sunlight is concentrated on a piece of paper by a spherical mirror or lens, then a hole can be burnt in it. For doing this, the paper must be placed at the focus of:

When sunlight is concentrated on a piece of paper by a spherical mirror or lens, then a hole can be burnt in it. For doing this, the paper must be placed at the focus of Concave mirror or convex lens.

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17

A diverging lens is used in:

 18

When an object is kept at any distance in front of a concave lens, the image foiled is always:

 20

A beam of parallel light rays is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the diagram below:


Which of the following could be inside the box?

 21

A beam of light is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the following figure:


The box contains: