Eduqas A-Level Physics A420QS
Basic Physics
Kinematics
Dynamics
Energy Concepts
Circular Motion
Vibrations
Kinetic Theory
Thermal Physics
Conduction of Electricity
Resistance
D.C. Circuits
Capacitance
Solids Under Stress
Electrostatic and Gravitational Fields of Force
Using Radiation to Investigate Stars
Orbits and the Wider Universe
The Nature of Waves
Wave Properties
Refraction of Light
Photons
Lasers
Nuclear Decay
Particles and Nuclear Structure
Nuclear Energy
Magnetic Fields
Electromagnetic Induction
Option A: Alternating CurrentsOption A
Option B: Medical PhysicsOption B
Option C: The Physics of SportsOption C
Option D: Energy and the EnvironmentOption D
Mathematical Requirements (Appendix C)
Wave Properties
Wavelength, slit width and the spread of the beam
- 3 things to know
- Component 3
Overview
Recall questions on diffraction depending on the ratio of wavelength to slit width, the condition for roughly semicircular spreading, the condition for a beam spreading through less than 180 degrees, and why a small loudspeaker spreads high notes more widely.
What you need to know
Answer each one before you reveal it.
State the condition for there to be very little diffraction at a slit.
Describe the wavefronts beyond a slit whose width is equal to or less than the wavelength.
Questions from this subtopic
Each one with the model answer underneath.
- 1
On what does the amount of diffraction at a slit depend?
Model answer
On the ratio of the wavelength to the width of the slit.
- 2
State the condition for there to be very little diffraction at a slit.
Model answer
The wavelength must be much smaller than the width of the slit.
- 3
Describe the wavefronts beyond a slit whose width is equal to or less than the wavelength.
Model answer
The waves spread as roughly semicircular wavefronts, filling the whole region beyond the slit.
- 4
Describe the beam beyond a slit whose width is greater than the wavelength.
Model answer
The main beam spreads through less than 180 degrees, so a distinct forward beam remains with the spreading confined to its edges.
- 5
What happens to the spread of the beam as the slit is narrowed at fixed wavelength?
Model answer
The beam spreads through a larger angle.
- 6
A wave of twice the wavelength passes through the same slit. How does its spread compare?
Model answer
It spreads through a larger angle, because the ratio of wavelength to slit width has doubled.
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