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JEE PHYSICS MCQ: ELECTROMAGNETIC WAVES
1
Medium
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Application
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A Laser beam is sent to the moon and reflected back to earth by ay mirror placed on the moon by an astronaut. If the moon is 384000 km from earth, how long does it take the light to make the round trip?
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Correct option: C
2.5 s
Option C (2.5 s) is correct because it is calculated by dividing the total distance (twice the distance to the moon) by the speed of light.
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Statement I: Sound waves are not electromagnetic waves.
Statement II: Sound waves require a material medium for propagation. For a plane electromagnetic wave propagating in x-direction, which one of the following combination gives the correct possible directions for electric field and magnetic field respectively? Assertion: The relative velocity of two photons travelling in opposite directions is the velocity of light.
Reason: The rest mass of photon is zero Intensity of electromagnetic wave will be The rms value of the electric field of the light coming from the Sun is . The average total energy density of the electromagnetic wave is Methane is a greenhouse gas because
Statement II: Sound waves require a material medium for propagation. For a plane electromagnetic wave propagating in x-direction, which one of the following combination gives the correct possible directions for electric field and magnetic field respectively? Assertion: The relative velocity of two photons travelling in opposite directions is the velocity of light.
Reason: The rest mass of photon is zero Intensity of electromagnetic wave will be The rms value of the electric field of the light coming from the Sun is . The average total energy density of the electromagnetic wave is Methane is a greenhouse gas because