The energy of a photon increases... Modern physics!

The energy of a photon increases as its wave- length decreases.
What is the energy of a microwave photon with a wavelength of 2.10 cm? Planck’s constant is 6.63 × 10−34 J · s and the speed of light is 3 × 108 m/s.
Answer in units of eV.

What is the energy of a visible photon with a wavelength of 4.90 × 10−7 m?
Answer in units of eV.

What is the energy of an X-ray photon with a wavelength of 3.60 × 10−8 m?
Answer in units of eV.

There's a very easy way to do these:

For energy E in eV and wavelength L in nanometers (nm)

E = 1240 / L

2.1 cm = 2.1 x 10^7 nm

So E = 1240/(2.1x10^7) eV

visible photon wavelength = 490 nm

So E = 1240/490 eV

x-ray wavelength = 36 nm

Thus E = 1240/36 eV