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  • Question
  • Light Emitting Diodes (LED) is used in fancy electronic devices such as toys emit


  • Options
  • A. X-rays
  • B. ultraviolet light
  • C. visible light
  • D. radio waves

  • Correct Answer
  • visible light 


  • Physics problems


    Search Results


    • 1. Pa(Pascal) is the unit for

    • Options
    • A. thrust
    • B. pressure
    • C. frequency
    • D. conductivity
    • Discuss
    • 2. Stars twinkle because

    • Options
    • A. the intensity of light emitted by them changes with time
    • B. the distance of the stars from the earth changes with time
    • C. the refractive index of the different layers of the earth's atmosphere changes continuously, consequently the position of the image of a start changes with time
    • D. the light from the star is scattered by the dust particles and air molecules in the earth's atmosphere
    • Discuss
    • 3. Natural radioactivity was discovered by

    • Options
    • A. Marie Curie
    • B. Ernest Rutherfor
    • C. Henri Becquerel
    • D. Enrico Fermi
    • Discuss
    • 4. One should not connect a number of electrical appliances to the same power socket because

    • Options
    • A. this can damage the appliances due to overloading
    • B. this can damage the domestic wiring due to overloading
    • C. this can damage the electrical meter
    • D. the appliance will not get full voltage
    • Discuss
    • 5. Rain is falling vertically downwards. To a man running east-wards, the rain will appear to be coming from

    • Options
    • A. east
    • B. west
    • C. northeast
    • D. southeast
    • Discuss
    • 6. Minimum number of unequal vectors which can give zero resultant are

    • Options
    • A. two
    • B. three
    • C. four
    • D. more than four
    • Discuss
    • 7. Moment of inertia is

    • Options
    • A. vector
    • B. scalar
    • C. phasor
    • D. tensor
    • Discuss
    • 8. Sound travels at the fastest speed in

    • Options
    • A. steel
    • B. water
    • C. air
    • D. vacuum
    • Discuss
    • 9. Planets do not twinkle because

    • Options
    • A. they emit light of a constant intensity
    • B. their distance from the earth does not change with time
    • C. they are very far away from the earth resulting in decrease in intensity of light
    • D. they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable
    • Discuss
    • 10. On a clean glass plate a drop of water spreads to form a thin layer whereas a drop of mercury remains almost spherical because

    • Options
    • A. mercury is a metal
    • B. density of mercury is greater than that of water
    • C. cohesion of mercury is greater than its adhesion with glass
    • D. cohesion of water is greater than its adhesion with glass
    • Discuss


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