Understanding Sound Waves,Ultrasound and the Electromagnetic Spectrum Physics Revision Lesson 2

In this lesson you will revisit: Sound waves (particularly ultrasound). Seismic Waves The Electromagnetic Spectrum

Sound Waves Can be reflected and refracted. Echoes are due to reflected sound. The amplitude of a sound wave is a measure of how much energy is being carried. Bigger amplitude means louder sound. Frequency of a sound determines its pitch. Frequency is measured in hertz. High frequency leads to high pitch and vice versa.

Wave Traces A high pitch sound. A low pitch sound. A quiet sound. A louder sound.

Ultrasound This is sound with a higher frequency than we can hear, i.e. above Hz. Uses include: industrial cleaning, breaking down kidney stones, industrial quality control, scanning of unborn babies and SONAR.

A louder sound. X rays are more energetic and penetrating and are a lot more dangerous, they could cause damage to the growing baby. Why do doctors use ultrasound to scan the foetus and not X rays which give a clearer picture? Ultrasound has many uses, especially in medicine where it is used to scan the foetus. 10 weeks20 weeks Using Sound Waves : Ultrasound

Seismic Waves (Earthquake Waves) During an earthquake the two types of wave that are released from the epicentre are primary waves (p-waves) and secondary waves (s-waves). Primary or p-waves are the fastest. They are longitudinal in nature and when they hit the surface they make objects and buildings vibrate vertically. They can travel through solids and liquids. Secondary or s-waves are the slowest. They are transverse in nature and when they hit the surface they make objects and buildings vibrate horizontally. They can only travel through solids.

You will need to know how seismic waves can tell us about the Earth’s structure. Outer core Crust Mantle Inner core Earth’s Structure

Electromagnetic Spectrum Although all e-m waves travel at the same speed, their wavelength [ ] and frequency [ƒ] can be different. The properties, dangers and uses of e-m waves depends on the wavelength [ ]. Waves that cook food. Waves that cause sun-tans.

Electromagnetic Spectrum Radio Micro Infra- Red Light Ultra- Violet X rays Gamma Wavelength ( ) increases Can you think of a phrase that would help you remember this order? Gate X Usually Lets In Most Radiation High frequency Short wavelength High energy Most penetrating High frequency Short wavelength High energy Most penetrating Low frequency Long wavelength Low energy Least penetrating Low frequency Long wavelength Low energy Least penetrating

Electromagnetic Spectrum

Uses and dangers of EM radiation Research the uses and dangers of the various radiations: RadiationUsesDangers Gamma X-rays Ultraviolet Light Infra red Microwaves Radio waves

EM Radiation: Uses: Dangers: Kills harmful bacteria in food, sterilising surgical equipment, killing cancer cells. High doses can kill cells. Lower doses can cause cells to become cancerous. Gamma

EM Radiation: Uses: Dangers: Shadow pictures of luggage and inside the human body. High doses can kill cells. Lower doses can cause cells to become cancerous. X rays Hospital workers limit exposure to Gamma and X rays by standing behind lead shields or by leaving the room when the radiations are being used. How do hospital workers limit their exposure to Gamma and X rays?

X rays X rays can penetrate soft tissue but not b_____. X rays are a_______ more by some materials than others. P________ f____ is used to detect X rays. one bsorbed hotographic ilm How are X rays slides formed?

EM Radiation: Uses: Dangers: Sun beds, fluorescent lamps and security marking. High doses can kill cells. Lower doses can cause cells to become cancerous. Ultraviolet Which type of radiation is the most dangerous? The higher the frequency of the radiation, the more dangerous it is. So gamma is more dangerous than X rays or ultraviolet.

Effects of EM radiation on living cells Infra red radiation is used in toasters, grills and radiant heaters. What effect do you think it has on your skin? Ultraviolet radiation can pass through skin to deeper tissues. What effect do you think the colour of the skin has on the amount of radiation that passes through it? The darker the skin, the more ultraviolet radiation is absorbed, the less can reach into deeper soft tissues.

EM Radiation: Uses: Dangers: Seeing and endoscopes Blindness Light

EM Radiation: Uses: Dangers: Remote controls (TV/VCR), radiant heaters, grills, optical fibre communication, night vision. Skin burns Infrared

Night vision All objects above absolute zero emit infrared radiation. The hotter an object is, the more heat radiation it emits. Some animals and cameras can detect infrared radiation and are able to build up a heat picture. Which are the hottest/coolest parts of the image shown? light is hot dark is cold

EM Radiation: Uses: Dangers: Satellite communication, mobile phone networks, cooking, RADAR. Internal tissue heating. Microwaves

Microwaves can be used in c_____ because many foods contain w____ molecules. Microwaves of the right w________ are able to make the water molecules r_______. This causes the food to get h____. How do microwaves cook foods? ooking ater avelength esonate otter

EM Radiation: Uses: Dangers: Communication and astronomy. Radio waves

How do radio signals from the UK reach around the globe? The longer wavelength radio waves from a transmitter reflect off the Earth’s outer atmosphere (ionosphere).

Getting hotter If electromagnetic radiation is incident upon a material what effects could it have? An alternating current could be induced in the material, with the same frequency as the incident radiation. The temperature of the material could increase. 21º C30º C50º C70º C

What is the upper range of human hearing? A.20 Hz B.200 Hz C Hz D Hz

What causes all sounds? A.Vibrations B.Reflections C.Refractions D.Heat

Which of the following can sound not travel through? A.Liquid B.Vacuum C.Solid D.Gas

A ship releases an echo sounding and 4 seconds later receives a signal from the seabed, how deep is the sea? (speed of sound in water is 1500 m/s) A.6000m B.375m C.750m D.3000m

Which of the following is not a use of ultrasound? A.Prenatal scanningPrenatal scanning B.Quality control in industryQuality control in industry C.Cleaning delicate machineryCleaning delicate machinery D.Cooking foodCooking food

EM Questions 1)Match up the following parts of the electromagnetic spectrum with their uses : Gamma raysAllow us to see Radio wavesRemote Controls Ultra Violet‘See’ broken bones VisibleCarry TV signals MicrowavesRADAR X raysSterilise equipment Infra RedCauses sun-tans

EM Questions 2) Which radiations are missing from below? Gamma AUltravioletLightInfrared BRadio waves A.___________ B.___________ X rays Microwaves