Electricity — Science STD 10 — Question

An object is 100mm in front of a concave mirror which produces an upright (erect image). The radius of curvature of the mirror is:

1. Less than 100mm.
2. Between 100mm and 200 mm.
3. Exactly 200mm.
4. More than 200mm

When the light is very bright, the diameter of pupil:

One coulomb charge is equivalent to the charge contained in:

A convex lens produces a magnification of +5. The object is placed:

1. At focus.
2. Between f and 2f.
3. At less than f.
4. Beyond 2f.

When a current flows through a conductor its temperature:

Which of the following can make a parallel beam of light from a bulb falls on it?

1. Concave mirror as well as concave lens.
2. Convex mirror as well as concave lens.
3. Concave mirror as well as convex lens.
4. Concave mirror as well as convex lens.

At noon the sun appears white as:

A burning candle whose flame is 1.5cm tall is placed at a certain distance in front of a convex lens. An image of candle flame is received on a white screen kept behind the lens. The image of flame also measures 1.5cm. If f is the focal length of convex lens, the candle is placed:

1. At f.
2. Between f and 2f.
3. At 2f.
4. Beyond 2f.

To determine the approximate value of the focal length of a given concave mirror, you focus the image of a distant object formed by the mirror on a screen. The image obtained on the screen, as compared to the object is always: