Skill Set 27.1

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Main Page > IB Physics Skill Sets > Skill Set 27.1

1. What is the frequency of a 2.0 m radio wave?

Alright, so the formula we'll be using here is:  \ V = F \lambda
 3 \times 10^8 \frac{m}{s} = F \times 2

\frac{3 \times 10^8}{2} = F

 \ F = 1.5 \times 10^8 Hz
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2. What is the energy in electron volts of a 150 nm photon?

Alright so lets find a formula we can use here.
We know that  E = hf \
and we know that \  f = c/\lambda
so we can substitute for frequency and we have \ E = hc/\lambda

when we put in our data, the equation looks like  E = \frac{(6.626 \times 10^{-34}) * (3 \times 10^8)}{(150 \times 10^{-9})}

then  E = 1.3252 \times 10^{-18} J

However we dont want our answer in Joules do we? So to convert into electron volts, we just divide by the amount of joules in an electron volt.

 \frac {(1.3252 \times 10^{-18} J)} {1.602 \times 10^{-19})} = 8.3 eV

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3. 400. nm light ejects photo-electrons from a metal that have a stopping potential of 1.17 V. What is the work function of the metal in electron volts?

4. How fast must an alpha particle (m = 6.64x10−27 kg) go to get within 5.0x10-15 m of an Iron nucleus (Z = 26)

5. What is the velocity of an electron with a wavelength of 12 nm?