Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    A diffraction grating has 300 lines per mm. It is illuminated with monochromatic light of wavelength 540nm. Calculate the angle of the 2nd order maximum giving your answer to the appropriate number of significant figures.

    So far i know you use the equation dsin(theta) = n-lambda and then rearrange for sin(theta), my calculations are 540*10^-9(*2)/3.3*10^-6 and then the answer i do is sin^-1(ans) to get the angle 1.875...*10^-11

    But the answer in the mark scheme is 18.9 degrees i dont understand what i did wrong, maybe its something obvious.
    Offline

    13
    ReputationRep:
    (Original post by RS012)
    A diffraction grating has 300 lines per mm. It is illuminated with monochromatic light of wavelength 540nm. Calculate the angle of the 2nd order maximum giving your answer to the appropriate number of significant figures.

    So far i know you use the equation dsin(theta) = n-lambda and then rearrange for sin(theta), my calculations are 540*10^-9(*2)/3.3*10^-6 and then the answer i do is sin^-1(ans) to get the angle 1.875...*10^-11

    But the answer in the mark scheme is 18.9 degrees i dont understand what i did wrong, maybe its something obvious.
    I think you have made an error in entering everything into your calculator. I have used the same numbers as you and got the correct answer. Your answer is quite far out for it to be simply due to your calculator being in radians, although I would also check to see if you're in degrees.

    I typed into my calculator:  \displaystyle \sin^{-1} \left(\frac{2 \times 540 \times 10^{-9}}{3.33 \times 10^{-6}}\right) and got the correct answer.
 
 
 
Poll
Favourite type of bread
Help with your A-levels

All the essentials

The adventure begins mug

Student life: what to expect

What it's really like going to uni

Rosette

Essay expert

Learn to write like a pro with our ultimate essay guide.

Uni match

Uni match

Our tool will help you find the perfect course for you

Study planner

Create a study plan

Get your head around what you need to do and when with the study planner tool.

Study planner

Resources by subject

Everything from mind maps to class notes.

Hands typing

Degrees without fees

Discover more about degree-level apprenticeships.

A student doing homework

Study tips from A* students

Students who got top grades in their A-levels share their secrets

Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.