What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

The expression for the wavelength of radiation is, 1/λ = R(1/n₁² - 1/n₂²)
Substitute values in the above expression, 1/λ = 109677 × (1/2² - 1/4²) = 109677 × (1/4 - 1/16) = 109677 × (3/16)
λ = 4.86 × 10⁻⁵ cm = 486 × 10⁻⁷ m = 486 nm.
The line belongs to bluish green colour.