Diffraction gratingsEdexcel International A Level Physics: Flashcards
What these 13 flashcards ask
- What is a diffraction grating?
- State the grating equation.
- What does d represent in the grating equation?
- How do you find d from the number of lines per millimetre N?
- What does n stand for in nλ = d sin θ?
- What is the path difference between waves from adjacent slits at angle θ?
- How do you find the highest order that can be seen?
- What does the central maximum look like in white light?
- In a first-order white-light spectrum, which colour is closest to the centre?
- What happens to the angle of the first-order maximum if d decreases?
- In Core Practical 6, how is the angle θ found from the measurements?
- What graph can be plotted to find λ in Core Practical 6?
- What safety precaution is needed when using a laser?
Exam questions on Diffraction gratings
- A student shines a red laser beam of wavelength 633 nm at normal incidence on a diffraction grating that has 300 lines per millimetre. A series of bright spots, called maxima, is formed on a distant screen.Calculate the highest order of maximum that can be seen on the screen.2 marks
- White light containing wavelengths from 400 nm (violet) to 700 nm (red) is directed at normal incidence at a diffraction grating with slit spacing 2.00 × 10⁻⁶ m. The light is then observed on a screen a long way from the grating.Calculate the angular separation between the first-order maxima for red light of wavelength 700 nm and violet light of wavelength 400 nm.2 marks
- In Core Practical 6 a student determines the wavelength of light from a laser. She uses a diffraction grating with 600 lines per millimetre at normal incidence, and places a screen 2.50 m from the grating. The first-order maximum is found 1.06 m from the central maximum on the screen.Describe how the student should set up the apparatus and take measurements so that she can calculate the wavelength accurately.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).