Waves Flashcards
What are the roles of waves
Transfer energy from one place to another
How to waves move
They Oscillate
What is the time period of a wave
The time it takes for one complete oscillation
Wave speed formula
Wave speed = Frequency x wavelength
Transverse wave movement
Oscillations are perpendicular to the direction of energy transfer
Examples of transverse waves
Light waves, physical waves
Longitudinal waves movement
Oscillations that are parallel to the direction of energy transfer
Longitudinal waves example
Sound waves and seismic waves
In reflection, angle of i = ?
Angle of incidence = angle of reflection
What is the normal
A line perpendicular from the surface
What is specular reflection
When the surface is flat and the normals are all in the same direction creating a clear image e.g. mirrors
What is scattered reflection
The surface is bumpy, normals are all different meaning we can’t see ourselves in the reflection
What is refraction
When waves change direction as they pass from a medium to new medium e.g. air into glass
What direction does the wave go when it enters a higher medium
The wave direction goes towards the normal
What direction does wave go when entering higher medium in a straight line
Continues in a straight line
What is the first step when drawing a ray diagram
Draw the normal at the point of incidence
What is the ray called in the more dense medium
Refracted ray
When ray goes from denser medium to less dense medium, what happens
It speeds up and bends away from the normal
What happens when white light is put through a triangular prism
The different colours of the rainbow bend at different degrees as they have different wave lengths
What is the law of refraction
When a wave enters a new medium, it changes direction
Law of reflection
Angle of incidence = angle of reflection
What are the conditions needed to TIR (Total internal reflection)
Angle of incidence > critical angle
-Going from a high refractive index to a low refractive index
Use of total internal reflection
Used in optical fibers
Used in cameras during keyhole surgery
What is the critical angle
The angle of incidence when the ray of refraction is 90 degrees, the ray causes TIR.
Describe the relationship between wavelength and refractive index for colours of the visible spectrum
-Refractive index decreases with an increasing wavelength
-Colours with a shorter wavelength refract more and bend more towards the normal.
What is meant by a frequency of 40kHz
-40,000 waves in one second.
Differences between sound and light waves
-Sound waves are longitudinal so they travel parallel to their source
-Light waves are transverse so they oscillate perpendicular to their source
-Light can travel in a vaccum, sound cannot.
Frequency range for human hearing
20Hz-20,000 Hz
Give the name of the device that detects ultrasound waves
A microphone
Describe how an oscilloscope is used to measure time period of ultrasound waves
-Adjust oscilloscope to obtain steady trace
-Adjust the time base to display one cycle of wave.
-Multiply the number of squares for one cycle by time base.
What is meant by the term total internal reflection.
When all the light is reflected and the angle of incidence is greater than the critical angle.
Explain the path of a ray of light through an optical fibre
-Total internal reflection
-Because optical fibre has higher refractive index than air
-Angle of i is greater than critical angle
Uses of gamma rays
-Sterilizing medical equipment
-Radiotherapy
-Treating cancer
Relationship between frequency and wavelength when wave at constant speed
-As one increases, the other decreases
(Non-linear)
Which colour on visible spectrum has the shortest wavelength
Violet
Dangers of ultraviolet radiation
-It can damage skin cells leading to skin cancer
Harmful effect of microwaves
-Can cause internal heating of body
