3. Waves Flashcards
What is wavefront
The peak of a transverse wave
The compression of a longitudinal wave
What is speed of wave
Distance travelled by a wave peak or trough every second
Unit m/s
What is frequency
The number of complete waves passing a point in one second
Unit hertz
What is wavelength
Distance from 1 wave peak to another
What is amplitude
The distance from the middle to the peak or the trough
The bigger the amplitude, the more energy it carries
How to calculate speed of wave
Wavelength x frequency
Unit m/s
Describe transverse wave
Vibrations are perpendicular to the direction in which the waves are traveling
Describe longitudinal waves
Vibrations are parallel to the direction in which the waves are traveling
Describe refraction when waves slow down
When water waves pass through shallow water
Wavefront crowded together so wavelength gets smaller
Waves slow down when pass from a less to a more dense material
When a wave is slowed down, it is refracted toward the normal
I>r
Describe refraction when a wave speed up
Wavefront spread out -> wavelengths gets larger
Move from a denser to a less dense material
It is refracted away from the normal
I
Describe diffraction
It is the spreading of waves when they pass through a gap or move past an obstacle
Narrower the gap, the more waves spread out and vice versa
Wavelength does not change on diffraction
For noticeable diffraction, the gap must be similar size to wavelength
Describe the image given by reflection
As far behind the mirror as the object is in the front
Same size as object
Laterally inverted ( left and right are swap around)
The image is virtual, cannot be focused on a screen
What is the law of reflection
Angle of incidence = angle of reflection
Describe the angle of refraction and incidence when light refract
Travel from less dense -> more dense
I > r
Travel from a more dense -> less dense
R> I
What is critical angle
The angle at which the refracted ray emerges along the boundary
What happen if i > or
I > critical angle -> the light ray is totally internally reflected
I refraction
How to calculate the refractive index
Speed of light in air / speed of light in medium
Sin I / sin r
Define refractive index
A measure of the change of direction of a light ray at non-normal incidence when it passes from air into the substance
What is the law of refraction
Refractive index = sin I / sin R
What is the principal focus
The point where parallel Ray directed straight at the converging lens are focused
What is the focal length
The distance from the lens to the principal focus
How does converging lens work
By changing the direction of light passing through it
When is a real and inverted image formed if light is directed through a converging lens
If the object is further from the lens than the principal focus is
When is the image real and diminish
When object is beyond 2F
Image is between F and the lens
