Question

X-rays are more harmful to human beings than ultraviolet radiations because X-rays:

• A. have frequency lower than that of ultraviolet radiations.
• B. have wavelength smaller than that of ultraviolet radiations.
• C. move faster than ultraviolet radiations in air.
• D. are mechanical waves but ultraviolet radiations are electromagnetic waves.

Hint:

X-rays are used in medical imaging but excessive exposure can damage tissues due to their high energy.

Answer 1

The Correct Option is B

X-rays and ultraviolet (UV) rays both belong to the electromagnetic spectrum, but X-rays have a much smaller wavelength and hence higher energy than UV rays. The energy of a photon is given by: \[ E = h f = \frac{h c}{\lambda} \] where:
\( E \) is energy,
\( h \) is Planck’s constant,
\( f \) is frequency,
\( c \) is the speed of light,
\( \lambda \) is the wavelength.

Since X-rays have a smaller wavelength (\(\lambda\)) than UV rays, they carry more energy per photon. This higher energy enables them to penetrate deeper into tissues, making them more harmful to living cells. Thus, the correct answer is (2).