physics question

hi, please could i have help on part 2 of this question? I know graident=hc and I've tried to work out the gradient like 5 times but I'm still not getting the correct answer!
I did: (3-1)*10*-19/ 1/3.7*10*6 - 1/2.7*10*6
here is the question: https://ibb.co/gwMz913
thank you!

Reply 1

Eimmanuel

Study Forum Helper

Original post

by anonymous56754

The values on the x-axis are like 2.0 × 10⁶ m^-1 NOT 1/(2.0 × 10⁶) m^-1 OR 1/2.0 × 10⁶ m^-1.

Spoiler

Reply 2

anonymous56754

Original post

by Eimmanuel

The values on the x-axis are like 2.0 × 10⁶ m^-1 NOT 1/(2.0 × 10⁶) m^-1 OR 1/2.0 × 10⁶ m^-1.

Spoiler

but isn't the x-axis 1/lamda?

Reply 3

helloos

Original post

by anonymous56754

but isn't the x-axis 1/lamda?

yes but the values on the x-axis are already in the 1/lamda form. it seems like you've mistaken the values on the x-axis for the values of lamda

Reply 4

Eimmanuel

Study Forum Helper

Original post

by anonymous56754

but isn't the x-axis 1/lamda?

Can you explain how does this make your calculation of gradient correct?

Is this 1/3.7*10*6 = 1/(3.7 × 10⁶) OR 1/3.7*10*6 = (1/3.7) × 10⁶?

Not sure why you post in maths forum when it is a physics problem on photoelectric effect.
Let talk about some physics.

Say we have a value of 3.5 on the x-axis. What does 1/λ mean?

$\dfrac{1}{\lambda} = 3.5 \times 10^6 \rightarrow \lambda = \dfrac{1}{3.5 \times 10^6} = 2.9 \times 10^{-7} \text{m}$
https://www.wolframalpha.com/input?i=1%2F%283.5*10%5E6%29

This wavelength corresponds to the uv region of the EM spectrum which is feasible for the photoelectric effect to occur.

If I use 1/λ = 1/3.5*10*6 = 1/(3.5 × 10⁶), this implies that the wavelength is 3.5 × 10⁶ m. This wavelength makes no sense in photoelectric effect.

This is what we call a sanity check of your working.

Reply 5

anonymous56754

Original post

by Eimmanuel

Can you explain how does this make your calculation of gradient correct?
Is this 1/3.7*10*6 = 1/(3.7 × 10⁶) OR 1/3.7*10*6 = (1/3.7) × 10⁶?
Not sure why you post in maths forum when it is a physics problem on photoelectric effect.
Let talk about some physics.
Say we have a value of 3.5 on the x-axis. What does 1/λ mean?
$\dfrac{1}{\lambda} = 3.5 \times 10^6 \rightarrow \lambda = \dfrac{1}{3.5 \times 10^6} = 2.9 \times 10^{-7} \text{m}$
https://www.wolframalpha.com/input?i=1%2F%283.5*10%5E6%29
This wavelength corresponds to the uv region of the EM spectrum which is feasible for the photoelectric effect to occur.
If I use 1/λ = 1/3.5*10*6 = 1/(3.5 × 10⁶), this implies that the wavelength is 3.5 × 10⁶ m. This wavelength makes no sense in photoelectric effect.
This is what we call a sanity check of your working.