waves Flashcards
What type of wave is visible light?
Transverse wave
Visible light is part of the Electromagnetic spectrum.
What are the two main types of waves discussed?
- Transverse waves
- Longitudinal waves
What happens during reflection?
A wave hits a boundary between two media and does not pass through, staying in the original medium.
What is refraction?
A wave passes a boundary between two different transparent media and undergoes a change in direction.
What is the law of reflection?
Angle of incidence (i) = Angle of reflection (r)
What is the normal line in the context of reflection?
A line at 90 degrees to the boundary.
What occurs when light moves from less dense to more dense media?
Light bends towards the normal.
What occurs when light moves from more dense to less dense media?
Light bends away from the normal.
What is the angle of incidence?
The angle of the wave approaching the boundary.
What is the angle of reflection?
The angle of the wave leaving the boundary.
What is the relationship between frequency and color in light?
Different frequencies account for different colors of light.
Fill in the blank: The reflection of a sound wave is called an _______.
echo
What equipment is used to investigate refraction?
- Ray Box
- Protractor
- Sheet of Paper
- Pencil
- Ruler
- Perspex blocks
What does Snell’s Law relate?
The angles of incidence and refraction to the refractive index of a medium.
What is the formula for Snell’s Law?
n = sini / sin r
What does the refractive index indicate?
The speed of light in the material relative to the speed of light in a vacuum.
What is the refractive index of diamond?
Approximately 2.4
What is the refractive index of glass?
Approximately 1.5
What are the two conditions for total internal reflection?
- Angle of incidence > critical angle
- Incident material is denser than the second material
True or False: The frequency of waves changes during refraction.
False
What should be used to draw perpendicular lines in experiments?
A set square
What can cause systematic errors in experiments?
Incorrectly drawn 90° lines
What should be done if the ray box light causes burns?
Run burns under cold running water for at least five minutes.
What is the purpose of the ray box in the refraction experiment?
To provide a narrow beam of light that can be easily refracted.
What is the critical angle?
The angle of incidence above which total internal reflection occurs.
What does a higher refractive index indicate about a material’s optical density?
The material is more optically dense.
What is the phenomenon called when all of the light is reflected instead of being refracted?
Total internal reflection
Total internal reflection occurs under specific conditions, which are explained in the following flashcards.
What are the two conditions for total internal reflection to occur?
- The angle of incidence is greater than the critical angle
- The incident material is denser than the second material
What happens when the angle of incidence is less than the critical angle?
Refraction occurs
What is the critical angle?
The angle of incidence at which light is refracted along the boundary
What is the relationship between critical angle and refractive index?
sin(c) = 1/n
In which applications is total internal reflection utilized?
- Optical fibres
- Endoscopes
- Prisms (e.g. periscopes)
How do optical fibres utilize total internal reflection?
They reflect light along the fibre for communications
What is a periscope?
A device consisting of two right-angled prisms used to see over tall objects
True or False: Total internal reflection can occur when light travels from a less dense material to a denser material.
False
What occurs at the glass-liquid boundary when the angle of incidence is greater than the critical angle?
Total internal reflection
What is the critical angle of opal if its refractive index is about 1.5?
42°
What is the critical angle of diamond if its refractive index is about 2.4?
25°
Fill in the blank: The larger the _______ of a material, the smaller the critical angle.
refractive index
What happens to light rays inside a material with a high refractive index?
They are more likely to be totally internally reflected
How does the critical angle of diamond compare to that of opal?
The critical angle of diamond is lower than that of opal
What conclusion can be drawn about the sparkle of diamond compared to opal?
Diamond appears to sparkle more due to more total internal reflection occurring
When calculating the critical angle, what is the first step using the refractive index?
Use the refractive index, n, to find sin(c)
What is the angle of incidence at which total internal reflection first occurs in the worked example?
65°
What are the two types of waves?
Transverse waves and Longitudinal waves
Define transverse waves
Waves that vibrate or oscillate perpendicular to the direction of energy transfer
What is the highest point of a transverse wave called?
Peak or Crest
What is the lowest point of a transverse wave called?
Trough
List examples of transverse waves
- Ripples on the surface of water
- Vibrations in a guitar string
- S-waves (a type of seismic wave)
- Electromagnetic waves (such as radio, light, X-rays etc)
Define longitudinal waves
Waves where the points along its length vibrate parallel to the direction of energy transfer
What are compressions and rarefactions in longitudinal waves?
- Compressions: Points that are close together
- Rarefactions: Points that are spaced apart
List examples of longitudinal waves
- Sound waves
- P-waves (a type of seismic wave)
- Pressure waves caused by repeated movements in a liquid or gas
What is amplitude?
The maximum or minimum displacement from the undisturbed position
What is wavelength?
The distance from one point on the wave to the same point on the next wave
How is frequency defined?
The number of waves passing a point in a second
What is the unit of frequency?
Hertz (Hz)
What is the time period (T) of a wave?
The time taken for a single wave to pass a point
What is the wave speed equation?
v = f × λ
What does the variable ‘v’ represent in the wave equation?
Wave speed in metres per second (m/s)
What does the variable ‘f’ represent in the wave equation?
Frequency in hertz (Hz)
What does the variable ‘λ’ represent in the wave equation?
Wavelength in metres (m)
What is the Doppler effect?
The apparent change in observed wavelength and frequency of a wave emitted by a moving source relative to an observer
What happens to the frequency of sound waves as an ambulance approaches?
It goes from a high pitch (high frequency) to a low pitch (low frequency) as the vehicle passes
List the types of radiation in the electromagnetic spectrum from longest to shortest wavelength
- Radio
- Microwave
- Infrared
- Visible
- Ultraviolet
- X-ray
- Gamma ray
What do all electromagnetic waves have in common?
- They are all transverse
- They can all travel through free space (a vacuum)
- They all travel at the same speed in free space
Fill in the blank: The wavelength of red light is _______ than that of violet light.
longer
What is the mnemonic to remember the order of colors in the visible spectrum?
Roy G. Biv
What is the order of colours in the visible spectrum from longest to shortest wavelength?
Red, Orange, Yellow, Green, Blue, Indigo, Violet
What mnemonic can help remember the order of the colours of visible light?
Roy G. Biv or Richard Of York Gave Battle In Vain
What is the electromagnetic spectrum usually given in order of?
Decreasing wavelength and increasing frequency
What type of waves are associated with long wavelengths?
Radio waves
What type of waves are associated with short wavelengths?
Gamma rays
What are the uses of radio waves?
- Broadcasting and communications
- Air traffic communication
- Mobile phone communication
What are the applications of microwaves?
- Cooking
- Satellite transmissions
What is infrared used for?
- Heaters
- Night vision equipment
- Security cameras
- TV remote controls
- Transport signals down fibre optic cables
What is visible light primarily used for?
- Optical fibres
- Photography
What is the main application of ultraviolet light?
Fluorescent lamps
What are the uses of X-rays?
- Observing internal structures of objects
- Medical applications
Fill in the blank: The process where certain substances absorb ultraviolet and re-emit it as visible light is known as _______.
fluorescence
What are the applications of gamma rays?
- Sterilising food
- Sterilising medical equipment
What effect does excessive exposure to microwaves have?
Heat damage to internal organs
What effect does excessive exposure to infrared light have?
Burning of the skin
What are the dangers of ultraviolet exposure?
- Skin cell damage
- Sunburn
- Blindness
What can gamma rays and X-rays cause?
- Cell death
- Cancer
- Cell mutations
As the frequency of electromagnetic waves increases, what happens to their energy?
It increases
What safety measure is used to prevent microwave radiation from escaping ovens?
Metal walls and metal grid in the glass door
What protective measures can be taken against infrared radiation?
Wearing protective clothing such as gloves
How can ultraviolet ray damage to the eyes be reduced?
Wearing sunglasses that absorb ultraviolet light
What is the purpose of radiation badges?
To monitor exposure to radiation for people working closely with it
True or False: Gamma rays are safe for human exposure.
False
explain path of light in optical fibre
total internal reflection because the core has higher refractive index than air, this is because angle of incidence is greater than critical angle.
difference between transverse and longitudinal wave
vibrations / oscillations;
correct relationship between direction of
travel/energy transfer and direction of vibration for
both transverse and longitudinal waves;
red and violet refractive index diffrence
red refracts less than violet;
red has a lower
refractive index than
violet
refractive index
decreases with
increasing wavelength
