The phenomenon of formation of three-dimensional image by the interference of two light beams from laser or other coherent sources of light is called :
(a) Optical photography
(b) X-ray photography
(c) Radiography
(d) Holography
Answer: (d) Holography
Explanation:
Holography is a technique that records the light scattered from an object and reconstructs it to display a three-dimensional image. It requires coherent light, often from a laser source, and involves interference patterns.
Consider the following statements :
1. Atom bomb is based upon the principle of uncontrolled nuclear fusion
2. Hydrogen bomb is based upon the principle of uncontrolled nuclear fission
3. Nuclear reactor is based upon the principle of controlled nuclear fission
Which of the statements given above is/are correct?
(a) 3 only
(b) 1 and 2
(c) 2 and 3
(d) 1, 2 and 3
Answer: (a) 3 only
Explanation:
Which of the following waves can propagate in a vacuum ?
1. Radio waves
2. Light waves
3. X-rays
4. Ultrasonic waves
Select the correct answer using the codes given below :
(a) 1, 2 and 3
(b) 1, 2, 3 and 4
(c) 2, 3 and 4
(d) 1 and 4
Answer: (a) 1, 2, and 3
Explanation:
Paper becomes brittle and yellow with age. Why?
1. The acid content in paper causes brittleness to develop
2. In the presence of visible light, photosensitised oxidation occurs
3. The ultra-violet component of sunlight causes photolysis of cellulose by direct cleavage of the cellulose polymer
(a) 1 and 2
(b) 2 and 3
(c) 1 and 3
(d) 1, 2 and 3
Answer: (d) 1, 2, and 3
Explanation:
Water kept in an old ‘surahi’ is less cold than the water in a new one. Why?
(a) The pores in the surahi help in evaporation of water
(b) The pores in the old surahi become clogged and thus, the total surface area for evaporation is reduced
(c) Old surahis become saturated with water and hence evaporation is not rapid
(d) Because of none of the above
Answer: (b) The pores in the old surahi become clogged, reducing surface area for evaporation.
Explanation:
Cooling in a surahi occurs due to evaporation, which absorbs heat. In an old surahi, the pores get clogged over time, reducing the efficiency of evaporation and, thus, the cooling effect.
The best conductor of electricity is :
(a) filtered hot water
(b) distilled water
(c) filtered water at room temperature
(d) salt water
Answer: (d) Salt water
Explanation:
Salt water contains ions (charged particles) that enable the flow of electricity. Distilled water lacks ions, and filtered water (even at various temperatures) does not conduct electricity as effectively.
Which of the following is the correct sequence of the regions of the sun as one moves from its core to the surface?
1. Photosphere
2. Chromosphere
3. Convection zone
4. Corona
(a) 1, 2, 3, 4
(b) 1, 3, 4, 2
(c) 2, 3, 4 1
(d) 2, 1, 3, 4
Answer: (a) 1, 2, 3, 4
Explanation:
The sequence is:
You are standing in a lift. The force on the floor of the lift due to your weight will :
(a) become zero when the lift moves up with an acceleration of
(b) become zero when the lift moves down with an acceleration of
(c) become zero when the lift moves with an acceleration of 9.8 in any direction
(d) remain unchanged whatever be the value of acceleration of the lift
Answer: (b) Becomes zero when the lift moves down with an acceleration of g (9.8 m/s²)
Explanation:
When the lift accelerates downward with the same acceleration as gravity (g = 9.8 m/s²), it creates a state of free fall. In this state, the normal force on the lift floor becomes zero, simulating weightlessness.
If the earth were 3 times as far from the sum as it is now, how would the gravitaltional attraction compare with its present value?
(a) The gravitational attraction would be 9 times its present amount
(b) The gravitational attraction would be double its present amount
(c) The gravitational attraction would be 1/9 of its present amount
(d) None of the above would be true
Answer: (c) The gravitational attraction would be 1/9 of its present amount
Explanation:
Two cars, passing each other at high speed, are in danger of side swiping because :
(a) of the increase in air pressure in the space between them
(b) of decrease in the velocity of air molecules between them
(c) of decrease in air pressure in the space between them
(d) increase in the velocity of air molecules between them
Answer: (c) Of decrease in air pressure in the space between them
Explanation:
According to Bernoulli's principle, as the relative speed of air between the cars increases, the pressure decreases. This creates a low-pressure zone, causing the cars to be drawn toward each other.
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