Q1. Optical fibre works on the principle of which of the following?
(a) total internal reflection
Q2. An endoscope is used by a physician to view the internal parts of a body organ. It is based on the principle of—
(a) refraction of light
(b) reflection of light
(c) total internal reflection of light
(d) dispersion of light
Q3. Which mirror is used as a rear view mirror in the vehicles?
(d) Plano concave
Q4. Which of the following is the best conductor of electricity?
Q5. What type of electromagnetic radiation is used in the remote control of a television?
(d) None of these
Q6. Transformer is used
(a) for converting AC into DC
(b) for coverting DC into AC
(c) to step up DC voltages
(d) to step up or step down AC voltages
Q7. Why Red light is used as danger signal?
(a) is scattered least
(b) is comfortable for eyes
(c) produces least chemical reactions
(d) absorbs least in air
Q8. Astronauts in space can’t stand at one place, because
(a) there is no gravity
(b) viscous forces of the atmosphere are very strong
(c) solar wind exert an upward force
(d) atmospheric pressure is very low
Q9. If the doors of a refrigerator are left open for a few hours, the room temperature will—
(c) remain the same
(d) decrease only in the area in the vicinity of the refrigerator
Q10. A body travelling with a speed of more than the velocity of sound in air is said to travel with—
(a) supersonic speed
(b) hypersonic speed
(c) ultrasonic speed
(d) infrasonic speed
Q11. The least distance of distinct vision for human eye is
(a) 25 cm
(b) 5 cm
(c) 75 cm
(d) 100 cm
Q12. Kerosene oil rises up in a wick of a lantern because of
(a) diffusion of the oil through the wick
(b) capillary action
(c) buoyant force of air
(d) the gravitational pull of the wick
Q13. Finger prints on a piece of paper may be detected by sprinkling fluorescent powder on the paper and then looking it into
(a) mercury light
(c) infrared light
(d) ultraviolet light
Q14. Which of the special technique is used in ships to calculate the depth of ocean beds?
(c) sonic boom
Q15. A body is thrown vertically upwards and then falls back on the ground. When its potential energy is maximum?
(a) on the ground
(b) at the maximum height
(c) during the return journey
(d) both on the ground and at the maximum height