Electromagnetic Waves

A parallel-plate capacitor of $50\ \mu\text{F}$ contains a dielectric slab of constant ($k$) with the same dimensions. If a time-varying potential difference is applied at a rate of $50\ \text{V/s}$. What is the…

The magnetic field in a travelling electromagnetic wave has a peak value of $20 \mathrm{nT}$. The peak value of electric field strength is

The atomic number (Z) of an element whose $k_a$ wavelength is $\lambda$ is 11. The atomic number of an element whose $k_a$, wavelength is $4 \lambda$ is equal to

Thermal radiation exist in which part of electromagnetic spectrum?

For a colour of light the wavelength for air is $6000 \AA$ and in water the wavelength is $4500 \AA$. Then the speed of light in water will be

In an electromagnetic wave, the electric and magnetising fields are $100 \mathrm{~V} / \mathrm{m}$ and $0.265 \mathrm{~A} / \mathrm{m}$. The maximum energy flow is

In which one of the following regions of the electromagnetic spectrum will the vibrational motion of molecules give rise to absorption?

X-rays and $\gamma$-rays of the same energies may be distinguished by

A laser device produces amplification in the

X-ray of wavelength $\lambda=2 \AA$ is emitted from the metal target. The potential difference applied across the cathode and the metal target is

Electromagnetic waves travel only through

A totally reflecting small plane mirror placed horizontally faces a parallel beam of light as shown in the figure. The mass of the mirror is $200 g$. Assume that there is no absorption in the lens and that $20%$ of the…