Waves Flashcards
What are Progressive Waves?
Waves that transfer energy away from a source.
What is a Longitudinal Wave?
A wave where the oscillations are parallel to the direction of energy transfer.
What is a Transverse Wave?
A wave where the oscillations are perpendicular to the direction of energy transfer.
What is the Wavelength of a Wave?
The distance in metres between two successive identical points on a wave, with the same pattern of oscillation.
What is the Period of a Wave?
The time taken in seconds for one complete pattern of oscillation to take place.
What is the Frequency of a Wave?
The number of oscillations per unit time.
What is the Displacement of a Wave?
The distance in meters any part of the wave has moved from its mean/rest position. (can be positive or negative)
What is the Amplitude of a Wave?
The Maximum displacement in meters.
In a Graphical Representation of a Longitudinal Wave, with pressure on the y-axis. What do peaks and troughs represent?
Peaks- Areas of Compression
Troughs- Areas of Rarefaction
How do you find the frequency of a wave on an oscilloscope?
Look at the time setting of the oscilloscope and e.g. 0.002 seconds per division. Then count the number of divisions that make up a period of the wave. Multiply this by the time base and inverse it to find the frequency of the wave.
How does the intensity of a wave relate to its amplitude?
Intensity is directly proportional to Amplitude Squared.
What is Reflection?
When waves rebound from a barrier, changing direction but remaining in the same medium
What is Refraction?
When waves change direction when they move from one medium to another, due to the difference in wave speed between each medium.
What is Diffraction?
When a wave spreads out after passing an obstacle or going through a gap.
Which EM waves are non-ionising?
Radio waves to visible light
What are the three types of UV and what do they do?
UV-A: Causes tanning
UV-B: Causes Cancers and Sunburn
UV-C: Filtered by atmosphere
What is a Plane-Polarised Wave?
A transverse wave that oscillates in only one plane
What is a polarising filter?
A filter that produces plane polarised light by selective absorption of one component of the incident oscillations. The filter transmits only the component of light polarised perpendicular to that direction.
What does Malus’ law state?
When a perfect polariser is put in a beam of polarised light, the intensity of the light that passes through is given by: I = I(max) cos2θ
What is Snell’s law?
n1sinθ1 = n2sinθ2
What is the critical angle with respect to total internal reflection?
The angle after which no refraction will take place and all incident waves will be reflected.
What does the principle of superposition state?
When two or more waves of the same type meet, the resultant wave can be found by adding the displacements of the individual waves.
What is interference?
The addition of two or more waves (superposition) that results in a new wave pattern. This can be constructive when waves travel at the same point in phase or destructive when two waves are in anti-phase.
What is coherence?
Two waves having a constant phase relationship.
What is path difference?
The difference in meters between the distances travelled by two waves arriving at the same point. It can be written in terms of wavelengths e.g. 1/4 λ
What is phase difference?
The difference in the phases of of two waves of the same frequency. Written as an angle e.g. 180° or π rad
What is Young’s double slit experiment?
An experiment demonstrating the wave nature of light via superposition and interference.
How is Young’s double slit experiment conducted?
A monochromatic red light source is placed behind a single slit. The wave then spreads out via diffraction, until it reaches another two parallel slits. Since the light is now coherent, waves from both slits are in phase so the waves will diffract in interfere with each other. This causes alternate bright and dark vertical bands to be shown on the screen
What is a diffraction grating and what is it used for?
It is a piece of optical equipment that enables light to be diffracted at different angles based off of the wavelength of the light and the separation of the grooves.
what are stationary/standing waves?
Waves that are in a fixed position with their energy in a fixed position.
How are stationary waves formed?
By, the interference of two waves travelling in opposite directions, with the same frequency and amplitude when they cross each other.
What are nodes on a stationary wave?
Points at which there is no displacement of the particles at any time.
What are antinodes on a stationary wave?
Points at which the displacement of the particles vary at the maximum amount.
