Sources of Energy — Science STD 10 — Question

To find the focal length of a concave mirror Rahul focuses a distant object with this mirror. The chosen object should be:

The real image formed by a concave mirror is larger than the object when object is:

1. At a distance equal to radius of curvature.
2. At a distance less than the focal length.
3. Between focus and centre of curvature.
4. At a distance greater than radius of curvature.

The size of the pupil of the eye is adjusted by:

1. Cornea.
2. Ciliary muscles.
3. Optic nerve.
4. Iris.

A virtual, erect and magnified image of an object is to be obtained with a convex lens. For this purpose,the object should be placed:

1. Between 2F and infinity.
2. Between F and optical centre.
3. Between F and 2F.
4. At F.

A good fuel is one which possesses:

1. High calorific value and low ignition temperature.
2. High calorific value and high ignition temperature.
3. High calorific value and moderate ignition temperature.
4. Low calorific value and moderate ignition temperature.

The stars appear higher in the sky than they actually are, due to:

Which of the following is used as a moderator in the reactor of a nuclear power station?

1. Liquid sodium.
2. Boron.
3. Graphite.
4. Carbon dioxide.

The mirror used by a dentist to examine the teeth of a person is:

A student is using a convex lens of focal length 10 cm to study the image formation by a convex lens for the various positions of the object. In one of his observations, he may observe that when the object is placed at a distance of 20 cm from the lens, its image is formed at (select the correct option):

One eV (electron volt) of nuclear energy is equivalent of:

1. 1.6 × 10⁻¹⁴J.
2. 1.6 × 10⁻¹²J.
3. 1.6 × 10⁻¹⁹J.
4. 1.6 × 10⁻¹³J.