Answer:
A λ = 97.23 nm
, B) λ = 486.2 nm
, C) λ = 53326 nm
Step-by-step explanation:
With that problem let's use the Bohr model equation for the hydrogen atom
 
 = -k e² /2a₀ 1/n²
 = -k e² /2a₀ 1/n² 
For a transition between two states we have
 
 -
 - 
 = -k e² /2a₀ (1/
 = -k e² /2a₀ (1/ 
 ² - 1 / n₀²)
² - 1 / n₀²)
Now this energy is given by the Planck equation
 E = h f
And the speed of light is
 c = λ f
Let's replace
 h c / λ = - k e² /2a₀ (1 / 
 ² - 1 / no₀²)
² - 1 / no₀²)
 1 / λ = - k e² /2a₀ hc (1 / 
 ² -1 / n₀²)
² -1 / n₀²)
Where the constants are the Rydberg constant 
 = 1.097 10⁷ m⁻¹
 = 1.097 10⁷ m⁻¹
 1 / λ = 
 (1 / n₀² - 1 / nf²)
 (1 / n₀² - 1 / nf²)
Now we can substitute the given values
Part A
 Initial state n₀ = 1 to the final state 
 = 4
 = 4
 1 / λ = 1.097 10⁷ (1/1 - 1/4²)
 1 / λ = 1.0284 10⁷ m⁻¹
 λ = 9.723 10⁻⁸ m
We reduce to nm
 λ = 9.723 10⁻⁸ m (10⁹ nm / 1m)
 λ = 97.23 nm
Part B
Initial state n₀ = 2 final state
 = 4
 = 4
 1 / λ = 1.097 10⁷ (1/2² - 1/4²)
 1 / λ = 0.2056 10⁻⁷ m
 λ = 486.2 nm
Part C
Initial state n₀ = 3
 1 / λ = 1,097 10⁷ (1/3² - 1/4²)
 1 / λ = 5.3326 10⁵ m⁻¹
 λ = 5.3326 10-5 m
 λ = 53326 nm