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Electromagnetic Waves — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves1 Mark
Question
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion: X-rays in vacuum travel faster than light waves in vacuum
Reason: The energy of X-rays photon is less than that of light photon.
✓

Answer

  1. A is false and R is also false.
Explanation:
All electromagnetic waves including X-rays travels with same velocity in vacuum. The energy of X-rays is greater than energy of the light because energy is inversely proportional to wavelength $\big(\text{E}=\frac{\text{hc}}{\lambda}\big)$ and wavelength of X-rays are smaller than light waves.

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