The physical quantity which does not change when X-rays of wavelength $10^{-10} m$, or visible light of wavelength 400 nm or radio waves of 500 m wavelength pass through glass is

frequency

The correct answer is Option (1) → frequency

When electromagnetic waves pass from one medium to another (here, from air to glass):

- The speed $v$ and wavelength $\lambda$ change according to $v = \frac{c}{n}$ and $\lambda = \frac{\lambda_0}{n}$, where $n$ is the refractive index.

- The frequency $f$ remains the same because it is determined by the source.

Correct answer: frequency