A student covered a torch with red cellophane sheet to obtain red light. Using the red light she obtains a shadow of an opaque object. She repeats this activity with green and blue light. Will the colour of the light affect the shadow ? Explain.
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How does the atomic hydrogen or oxy-hydrogen torch function for cutting and welding purposes? Explain.
Atomic hydrogen atoms are produced by the dissociation of dihydrogen with the help of an electric arc. This releases a huge amount of energy (435.88 kJ mol–1 ). This energy...
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Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher's advice?
Laser light is harmful for the human eyes, because its intensity is very high. It can cause damage to the retina and lead to blindness. Hence, it is advisable not...
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Boojho made light from a laser torch to fall on a prism. Will he be able to observe a band of seven colours? Explain with a reason.
No, laser torch gives out light of only one colour
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The concave reflecting surface of a torch got rusted. What effect would this have on the beam of light from the torch?
The beam of light will be diffused with lower intensity
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A student had a ball, a screen and a torch in working condition.
Some of the reason can be (i) The screen is away from the ball. (ii) The beam of light from the torch is falling parallel to the screen on the ball. (iii) The...
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A torch is not functioning, though contact points in the torch are in working condition.
The possible reason could be (i) the bulb may be fused. (ii) the cells may have been used up. (iii) the cells are not placed in the correct order. (iv) the switch is faulty....
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A battery-operated torch is adjusted to send an almost parallel beam of light.
The correct answer is (a) 40 lux
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When an unpolarized light of intensity I_0 is incident on a polarizing sheet, the intensity of the light which does not get transmitted is
The correct answer is (1) When unpolarised light of intensity Io is incident on a polarizing sheet, only Io/2 is transmitted.
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If the speed of light is 3.0 × 10^8 ms^-1 ,calculate the distance covered by light in 2.00ns.
Distance covered = speed ×time =3.0 × 108 m s-1 ×2.00 ns =3.0 × 108 m s-1 × 2.00 ns × 10-9 s/1ns =0.600 m
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The Sixth and the Eighth Five Year Plans covered the period 1980-1985 and 1992-1997 respectively. The Seventh Five Year Plan covered the period:
(c) Period between 1990-92 was second plan holiday. The first plan holiday was between 1966-69.
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