3 Waves Flashcards by Ankita Somisetty

Transverse Waves - oscillations

Oscillations are perpendicular to the direction of energy transfer

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Longitudinal Waves - oscillations

Oscillations are parallel to the direction of energy transfer

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Example of Transverse Waves

Electromagnetic Waves
e.g. light

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Example of Longitudinal Waves

Sound waves

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Amplitude

Height of the wave

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Wavefront

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Frequency

Number of complete waves per second

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Wavelength

The distance for one complete wave

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Time Period

Time for one complete wave

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What do waves transfer/not transfer

Transfer energy and information without transferring matter

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Equation for Wavespeed

Frequency x Wavelength

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Equation for Frequency

1/ Time Period

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What can be done to all waves

Reflected
Refracted

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Doppler Effect

There is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer

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What is light part of?

A continuous spectrum -> electromagnetic spectrum

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Order of electromagnetic spectrum

Increasing frequency / low wavelength

Radio Waves
Microwaves
Infrared Radiation
Visible Light (ROYGBIV)
Ultraviolet
X-Ray
Gamma Rays

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Uses of Radio Waves

broadcasting and communications

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Uses of Microwaves

cooking and satellite transmissions

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Uses of Infrared Radiation

heaters and night vision equipment

Uses of Visible Light

optical fibres and photography

Uses of Ultraviolet

fluorescent lamps

Uses of X - Rays

observing the internal structure of objects and materials, including for medical applications

Uses of Gamma Rays

sterilising food and medical equipment

Dangers of microwaves

internal heating of body tissue

Dangers of Infrared Radiation

skin burns

Dangers of Ultra Violet

damage to surface cells and blindness

Dangers of Gamma rays

cancer, mutation

Law of Reflection

the angle of incidence = the angle of reflection

Refraction

A change in direction of a wave passing from one medium to another due to a change of speed

What happens when a light ray is passing from a medium of low refractive index (e.g. air) to a medium of high refractive index (e.g. water)?

Fast -> Slow Water has a higher refractive index + more optically dense than air. So refracted ray bends towards normal

What happens when a light ray is passing from a medium of high refractive index (e.g. water) to a medium of low refractive index (e.g. air)?

Slow -> Fast Air has a lower refractive index + less optically dense than water. So refracted ray bends away from the normal

Formula for Refractive Index

Refractive index = sin (angle of incidence)/sin(angle of refraction)

Critical Angle

When the angle of incidence is greater than the critical angle, the light ray stops being refracted and is totally internally reflected (TIR)

Formula for critical angle

sin (critical angle) = 1/refractive index

Total internal reflection in a prism - use

Reflectors on the back of vehicles Reflective clothing

Total internal reflection in optical fibres - use

Fibre broadband (communications) Endoscopes

Frequency range for human hearing

20 Hz - 20 000 Hz | Upper limit decreases with age

Investigating the speed of sound in air

2 people stand 100m away from eachother Person A should clap their hands Person B should use a stopwatch (start when they see person A clap hands and stop when they hear the sound) Speed = distance/time Repeat with multiple distances

Frequency and pitch

As frequency increases, pitch increases

Amplitude and loudness

As amplitude increases, loudness increases

Practical: investigate the frequency of a sound wave using an oscilloscope

1. Connect 2 microphones to an oscilloscope and place them 2m apart 2. Clap 3. Find the time difference between the 2 peaks of the 2 graphs for the 2 microphones 4. Speed = distance/time

Characteristics of all electromagnetic waves

* Travel at the speed of light = 3 x 10 to the power of 8 * All are transverse * Can travel in a vacuum/don't need a medium * Can be reflected + refracted

Total Internal Reflection (TIR)

* All reflection is inside the material * All the light is reflected * Occurs when the angle of incidence is greater than the critical angle

Virtual Image

* Cannot be formed on a screen * Laterally inverted

Conditions for Total Internal Reflection

* Light travels froma. more optically dense to a less optically dense medium (slow-> fast) * i>c