## Homework Problem #7

$c=\lambda v$

Posts: 21
Joined: Fri Sep 28, 2018 12:26 am

### Homework Problem #7

1.7 (a) The frequency of violet light is 7.1 1014 Hz. What
is the wavelength (in nanometers) of violet light? (b) When an electron beam strikes a block of copper, x-rays with a frequency of 2.0 1018 Hz are emitted. What is the wavelength (in picometers) of these x-rays?

ChathuriGunasekera1D
Posts: 78
Joined: Fri Sep 28, 2018 12:17 am

### Re: Homework Problem #7

(a) Using the equation c = λ * v (λ is wavelength, v is frequency, c is the speed of light), you can sub in what you know!

3.0 x 10^8 m/s = (7.1 x 10^14 s^-1) x (λ)
λ = 4.225 x 10^-7 m and they want it written in nanometers so it become 422.5 nm. And because 422.5 nm falls on the violet light wavelength area, the answer is correct!

(b) We use the same equation for this one too!

3.0 x 10^8 m/s = (2 x 10^18 s^-1) x (λ)
λ = 1.5 x 10^-10 m and converted to picometers (10^-12 m) is 150 pm.