Magnetic Effects of Electric Current — Science STD 10 — Question

The image of an object formed by a plane mirror is:

Which of the following changes occur when you walk out of bright sunshine into a poorly lit room?

1. The pupil becomes larger.
2. The lens becomes thicker.
3. The ciliary muscle relaxes.
4. The pupil becomes smaller.

The resistivity of copper metal depends on only one of the following factors. This factor is:

1. Length.
2. Thickness.
3. Temperature.
4. Area of cross-section.

One MeV of nuclear energy is equivalent to:

1. 1.6 × 10⁻¹³J.
2. 1.6 × 10⁻¹⁹J.
3. 1.6 × 10⁻¹⁶J.
4. 1.6 × 10⁻¹⁵J.

The frequency of alternating current (a.c.) supply in India is:

A 10mm long awl pin is placed vertically in front of a concave mirror. A 5mm long image of the awl pin is formed at 30cm in front of the mirror. The focal length of this mirror is:

1. -30cm.
2. -20cm.
3. -40cm.
4. -60cm.

The commercial unit of energy is:

1. Watt.
2. Watt-hour.
3. Kilowatt-hour.
4. Kilo-joule.

The image formed by a concave mirror is real, inverted and highly diminished (much smaller than the object). The object must be:

1. Between pole and focus.
2. At focus.
3. At the centre of curvature.
4. At infinity.