What will be the photon energy in Joule if it has wavelength 2000 Å?

CONCEPT:

• The photon is a type of elementary particle. It is a basic unit of light. Photons are massless, and they always move at the speed of light in a vacuum ( c = 3 × 108  m/s)
• Photon energy is the energy that is carried by a single photon. The amount of this energy is inversely proportional to the wavelength.
  • If the wavelength increases, energy will be lowered.

The equation of photon energy is given by:

\(E=\frac{hc}{λ}\)

where E is energy, h is the Planck constant, c is the speed of light in a vacuum and λ is the photon's wavelength. In this equation h and c both are constants.

CALCULATION: 

Given that λ = 2000 Å = 2000 × 10-10 m

h = 6.626 × 10-34  (constant)

c =  3 × 108   (constant)

E = (h × c) / λ 

E = 6.626 × 10-34 × 3 × 108 / 2000 × 10-10

E = 9.94 × 10-19 J

The correct answer is Option 4 i.e. 9.94 × 10-19 J