Electromagnetic radiation of highest frequency is

Which of the following waves is used in a speed gun to measure the speed of a ball in a cricket match?

What protects us from $UV$ light emitted by the Sun?

Electromagnetic waves with wavelengths ranging from $3 \times 10^{-3} \, m$ to $1 \, m$ are used in satellite communication. What is the corresponding frequency range? (Given $c = 3 \times 10^8 \, m/s$)

Write the sources of microwaves and infrared waves and their uses.

$A$ monochromatic source of light operating at $15 \text{ kW}$ emits $2.5 \times 10^{22} \text{ photons/s}$. The region of an electromagnetic spectrum to which the emitted electromagnetic radiation belongs to . . . . . . . (Take $h = 6.6 \times 10^{-34} \text{ J}\cdot\text{s}$ and $c = 3 \times 10^8 \text{ m/s}$).