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WR2 The Electromagnetic Spectrum

We have already studied the electromagnetic spectrum in S3. This will now be revised.

WR 2-1 What do we know already?

A. ORGANISE

The whole class needs to divide into 7 groups

B. ENGAGEIn your group, examine each of the images on the electromagnetic energy

cards. Place the cards in a sequential order. Explain why you chose the order you did to your group, and be prepared to explain it to the whole class (you may want to choose a REPORTER for your group who will verbally give your information back to the whole class).

WR 2-2 Demonstrations and Effects

EXPERIMENT WR 3A -Visible light splits up and what is infrared anyway?Your teacher will demonstrate the splitting of white light using a triangular prism,

What order are the colours in and how does this relate to frequency and wavelength?

Your teacher will also look for another type of radiation. Where is it in relationship to the colours in the visible light spectrum

Your teacher will discuss uses of infrared radiation with you after the demonstration.

EXPERIMENT WR 3B - Ultraviolet - what is it good for?This may be demonstrated or you may have a chance to do some of this yourself.

Westhill Academy MJR Waves & Radiation (National 5) 7

Raybox

White light ray

Triangular prism

Thermopile or IR probe

Multimeter

NASA eClips TM Making Waves Teacher Gudie(modified)

WARNING: UV RAYS CAN BE HARMFUL; UNDER NO CIRCUMSTANCES SHOULD YOU DIRECT UV LIGHT TOWARDS YOUR EYES.

Try directing a UV light source towards a banknote or the front and/or back of a bank card and observe what happens, there may be some other items available to try this with.

EXPERIMENT WR3C - The bare bones of X RaysYou will now have the chance to examine some X-ray photographs - NOTE : these are not the X rays themselves, they are images created using the x rays.

EXPERIMENT WR 3D - Even smaller = Gamma RaysYour teacher will now show you a demonstration about the penetrating ability of gamma rays. WARNING: Your teacher will be using radioactive material so listen

carefully to ALL safety instructions they give to you. (You will come back to study other types of radiation in more detail at the end of unit 2).

If you get a chance, either in school or at home you can study how Radiotherapy is carried out using the animation on this site:

http://www.insidestory.iop.org/insidestory_flash1.html

Westhill Academy MJR Waves & Radiation (National 5) Page 18

http://www.insidestory.iop.org/insidestory_flash1.html

WR2-3 Exploring the Spectrum in more Detail

As a group copy and complete the following table in your ROUGH JOTTER by researching one segment of the electromagnetic spectrum in detail. You can use information from the demonstrations just given, books and/or the internet. EACH GROUP SHOULD DO A DIFFERENT MEMBER OF THE SPECTRUM. This may be done in class, or at home, or both.

Section of

Spectrum

Wavelength span

(m)

Frequency span

(Hz)Energy span (J)

Where humans

use them (1

medical and 1

industrial/

domestic)

Emitter of this

radiation

Detector of this radiatio

n

Example of something that is the same size

as one wavelengt

h

Your teacher will now allow you to contribute to a class discussion where we bring some organisation to all of this data and ideas you have collected, we will consider the following questions;

1. What quantity are the electromagnetic waves transferring from the source to their final destination?

2. What is the correct order of the members of the electromagnetic spectrum?

3. How fast are these waves?4. What happens to the value of the wavelength as you move from radio

waves to gamma rays?5. What happens to the value of the frequency as you move from radio

waves to gamma rays?6. What happens to the amount of energy associated with each section of

the electromagnetic spectrum as you move from radio waves to Gamma rays?

7. What type of mathematical relationship exists between wavelength and frequency?

8. What type of mathematical relationship must exist between energy and frequency?


NASA eClips TM(modified)

NASA eClips TM Making Waves Teacher Gudie(modified)

WR 2-4 Thinking about What We Found OutUse the data collected by the class, the discussion and the information given to copy and complete the following notes in your notes jotter;

The Electromagnetic Spectrum

Section of

Spectrum

Wavelength span

(m)

Frequency span (Hz)

Energy Span (J)

Where humans

use them

Emitter of this

radiation

Detector of this

radiation

Example of

something that is the same size as

one waveleng

th

All members of the electromagnetic Spectrum travel at _____________ m/s which is the same as the ________ __ _______ in a vacuum (or air). They are waves, which in common with all other waves, transfer ___________ from one location to another, however members of the electromagnetic spectrum do not require a _________ to travel through.

As you travel from ____________ to _____________ the wavelength becomes ____________.

As you travel from __________ to _______________ the frequency becomes ______________.

continued


7 rows

<label these ? with Frequencies>

<label these ? with Wavelengths>

NASA eClips TM(modified)

NOTES

Gamma Rays X Rays UV IR Micro-

wavesTV Radio

?? ?? ?

? ?

????

???

visib

le li

ght

Maths and Electromagnetic Waves

Looking at the maths of this situation can help you see the relationship between wavelength and frequency;

we know that for all waves v = f λ

If we rearrange this we get From S3 we know that all of the electromagnetic spectrum members travel at the same speed as light when they are in a vacuum (3x108m/s) which means that it is a constant for all of these waves,

so

This means that the wavelength is inversely proportional to the frequency,

i.e. as the frequency decreases, the wavelength increases and vice versa!

Energy and Frequency

As you travel from _________ waves to ______________ ________the energy of the waves ___________, so does the ____________, so there must be a mathematical relationship between them.

This means E f


NOTES

We remove the proportionality symbol and insert an equals and a constant. This constant has a precise value and is called Plancks constant (h) = 6.63 x 10-34 Js

E = hf

NB: This energy formula does not need to be known for Nat 5 (it will for Higher), however the fact that ENERGY INCREASES AS THE

FREQUENCY INCREASES does have to be known.


WR2-5 Technology and the Electromagnetic SpectrumWatch the video segment on the Launchpad: The Fermi Gamma Ray Space Telescope (4:32 mins), it can be found here if you are doing this activity at home;http://www.nasa.gov/audience/foreducators/nasaeclips/launchpad/index.htmlscroll down and select the correct video.(If subtitles are required, you must use the online version - click on the faint grey ‘CC’ option at the bottom right of the video screen’s frame).

Read the following Supplementary Information

The universe is home to many strange and beautiful phenomena. Some of these spectacles can generate huge amounts of energy. Super massive black holes, merging neutron stars, streams of hot gas moving close to the speed of light . . . these are but a few of the marvels that generate gamma-ray radiation. Gamma rays are the most energetic form of radiation. These rays are billions of times more energetic than the type of light visible to our eyes. What is happening to produce this much energy? What happens to the surrounding environment near these phenomena? How will studying these energetic objects add to our understanding of the nature of the Universe and how it behaves?

The Fermi Gamma-ray Space Telescope, formerly GLAST, will open this high-energy world to exploration and help us to answer these questions. With Fermi, astronomers will have a superior tool to study black holes. Notorious for pulling matter in, black holes can accelerate jets of gas outward at fantastic speeds. Physicists will be able to study subatomic particles at energies far greater than those seen in ground-based laboratories. Cosmologists will gain valuable information about the birth and early evolution of the Universe.

The Fermi mission has several objectives:

Explore the most extreme environments in the Universe, where nature harnesses energies far beyond anything possible on Earth.

Search for signs of new laws of physics and what composes the mysterious dark matter.

Explain how black holes accelerate immense jets of material to nearly light speed.

Help crack the mysteries of the stupendously powerful explosions known as gamma-ray bursts.

Answer long-standing questions across a broad range of topics, including solar flares, pulsars and the origin of cosmic rays.

Little is known about gamma rays. Because of its unique instruments and position, Fermi will help scientists learn more about this unexplored electromagnetic radiation. Fermi will help scientists make advances in astronomy and high-energy physics. International scientists hope the powerful


Figure 1. Fermi Gamma-ray Space Telescope exploring space. Image credit: NASA

http://www.nasa.gov/audience/foreducators/nasaeclips/launchpad/index.html

telescope may also yield unanticipated findings about black holes and dark matter.

Source: Fermi Gamma-ray Space Telescope Home Page http://fermi.gsfc.nasa.gov/

Vocabularyblack hole – A black hole is a region of space with gravitational force so strong that nothing can escape from it.cosmologist – A cosmologist is a scientist or astronomer who studies large scale structures and dynamics of the universe, including the origins of the universe.dark matter – Dark matter is the name given to the amount of mass whose existence is deduced from the analysis of galaxy rotation curves but which until now has escaped all detection. There are many theories about dark matter, but the subject is still a mystery.electromagnetic radiation – Electromagnetic radiation is energy radiated in the form of waves. It consists of electric and magnetic fields travelling at the speed of light.Fermi Gamma-ray Space Telescope – Fermi is a space telescope that consists of two parts: the Large Area Telescope, or LAT, and the Fermi Burst Monitor. The LAT has a wide field of view and can detect gamma rays. The Fermi Burst Monitor observes gamma ray bursts which are sudden, brief flashes of gamma radiation that occur about once a day.frequency (f) – Frequency is the number of waves that pass a fixed point in a given period of time. The frequency of electromagnetic radiation is measured in hertz (Hz) which is defined as the number of waves per second.Joule (J) – The joule is a unit of energy. One joule is the energy expended when 1 Newton of force is applied to move an object a distance of 1 meter.neutron star – A neutron star is the type of star formed when a massive star explodes as a supernova, leaving behind an ultra dense core.photon – A photon is a quantum, or discrete amount, of light energy. Photons have no mass and behave like both a particle and a wave.Planck’s constant (h) – Planck’s constant is a physical constant relating the energy of a photon to its frequency. The value of this constant is approximately 6.626 x 10-34 joule second.pulsar – A pulsar is a rotating neutron star which generates regular pulses of radiation.solar flares – Solar flares are violent eruptions of gas on the sun’s surface.speed of light (c) – The speed of light is the speed of electromagnetic radiation in a perfect vacuum. The speed of light is the same for all frequencies of electromagnetic radiation, 3.0x108 m/s.wavelength – Wavelength is the length of one wave of radiation, or the distance between two consecutive waves. Wavelength is usually measured in meters.

Discuss1. Compare and contrast electromagnetic waves with other kinds of waves

e.g. sound, water, earthquake (S and P waves)…etc..

2. Discuss and compare limitations for applications of e-m waves in relation to frequency.


NASA eClips TM Making Waves Teacher Guide

3. Explain how observing an object through different wavelengths provides significantly more information than an image of the object in only one type of electromagnetic radiation. Give an example.

4. Why are astronomers interested in searching for and studying gamma rays? What can they learn from this study?

5. How does technology enhance the study of gamma rays? Give specific examples.

WR2-6 Calculations and the Electromagnetic SpectrumWe have already seen that we can use the wave equation and our speed-distance time equation for our wave calculations, we can also use the new equation E = hf to deal with electromagnetic waves.

Equation Summary for the Electromagnetic Spectrum

We can use the following equations when we deal with electromagnetic waves

v=fλ E = hf

Question Practice on EM Wave Calculations

1. Find the shortest wavelength associated with visible light from the information gathered in class. Using this value and the information above, calculate the associated frequency. Does the value you calculated agree with the value given in class?

2. Find the lowest frequency associated with visible light from the information gathered in class. Using this value and the information above, calculate the associated energy. Does the value you calculated agree with the value given in class?

3. Perform the following calculations. In which part of the electromagnetic spectrum can each wave be found?a. The wavelength of radiation with a frequency of 610 kHz.b. The wavelength of radiation with a frequency of 2.34x1018 Hertzc. The frequency of radiation with a wavelength of 10.5 nm. d. The frequency of radiation with a wavelength of 1520 m.e. The energy of radiation with a frequency of 6.51x1014 hertzf. The energy of radiation with a wavelength of 820 nm.


NOTES

Q 1-3 NASA eClips TM Making Waves Teacher Guide

NASA eClips TM Making Waves Teacher Guide(modified)

4. A student writes the following statements about electromagnetic waves.I Electromagnetic waves all travel at the same speed in air.II Electromagnetic waves all have the same frequency.III Electromagnetic waves all transfer energy.Which of these statements is/are correct?

A I onlyB II onlyC I and III onlyD II and III onlyE I, II and III

5. A water wave is diffracted when it passes through a gap in a barrier. The wavelength of the wave is 10 mm. The gap is less than 10 mm.

(a) Copy and complete the diagram above to show the pattern of the wave to the right of the barrier.

(b) The diagram below represents the electromagnetic spectrum.

(i) Identify radiation A.(ii) Apart from diffraction, state one property that all

electromagnetic waves have in common.

6. A television company is making a programme in China.Britain receives television pictures live from China. The television signals

are transmitted using microwaves. The microwave signals travel from China via a satellite, which is in a geostationary orbit.

The frequency of the microwave signals being used for transmission is 8 GHz.

(a) What is the speed of the microwaves?(b) Calculate the wavelength of these microwaves.

7. A team of astronomers observes a star 200 light-years away.Images of the star are taken with three different types of telescope as

shown.


SQA National 5 Specimen Question paper Q9

SQA National 5 Specimen Question paper Q9

SQA 2008 S Grade Credit Q2(c) (modified)

(a) Explain why different types of telescope are used to detect signals from space.(b) Place the telescopes in order of the increasing wavelength of the

radiation which they detect.(c) State a detector that could be used in telescope C.

8. The diagram represents the electromagnetic spectrum.Some of the radiations have not been named.

(a) (i) Name radiations P and Q.(ii) What quantities could be represented by the arrows A and B?

(iii) Which radiation in the electromagnetic spectrum has the shortest wavelength?

(iv) State one detector of radio waves. (v) State one medical use of infrared radiation. 8 (b) Yellow light is part of the visible spectrum. The wavelength of yellow light is 5.9 x10–7m.

The visible spectrum also contains red, blue and green light.Use the information above to complete the following table.

9. The diagram below represents the electromagnetic spectrum.

(a) Identify radiation A.(b) Apart from diffraction, state one property that all electromagnetic

waves have in common.


SQA 2008 S Grade Credit Q14(b) (modified)

Telescope A - Visible light

Telescope B - Infrared Telescope C - X rays

SQA 2010 S Grade Credit Q14 (modified)

A

B

(c) Copy and complete this sentence by selecting the correct words.“Compared to infrared radiation, microwaves have a

longer/shorter wavelength which means they have a higher/lower frequency.”

10. Glass transmits infrared radiation and visible light. The percentage transmitted depends on the type

and thickness of the glass. The data from tests on two different types of glass is displayed in the graph.

A glass conservatory is being built on a house. The homeowner wants the inside of the conservatory to remain as cool as possible throughout the summer.

Using information from the graph, explain which type of glass should be used.


SQA National 5 Specimen Question paper Q4 (c)

SQA National 5 Specimen Question paper Q6 (b) & Q11 (c)

11. The Sun produces electromagnetic radiation. The electromagnetic spectrum is shown in order of increasing wavelength. Two radiations P and Q have been omitted.

(a) (i) Identify radiations P and Q.(ii) The planet Neptune is 4·50 × 109 km from the Sun. Calculate

the time taken for radio waves from the Sun to reach Neptune.(iii) State what happens to the frequency of electromagnetic

radiation as the wavelength increases.(b) The Sun produces a solar wind consisting of charged particles. In

one particular part of the solar wind, a charge of 360 C passes a point in space in one minute. Calculate the current.

12. A ray of green light strikes a triangular prism as shown.

(i) Copy and complete the diagram to show the path of the ray of green light as it passes through the prism and on to the

screen.(ii) The green light is now replaced by white light.

Describe what is now observed on the screen.(iii) State one colour which has a longer wavelength than green

light.


SQA 2011 Int 2 Q29

SQA 2008 S Grade General Q20 (a)

13. Different types of radiation are used to detect and treat illnesses and injuries.

Four of these radiations areinfrared laser light ultraviolet X-rays

(a) What type of radiation is used to treat skin conditions such as acne?

(b) (i) State one medical use of X-rays.(ii) What can be used to detect X-

rays?

(c) Colour photographs called thermograms are used to find the temperature variation in a patient’s

body. Name the radiation used to make

thermograms.

(d) Explain why people need to be protected from overexposure to ultraviolet radiation


SQA 2007 S Grade General Q10

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