Speed of Sound. 2. How long will it take sound to travel a distance of 200 m?

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1 Speed of Sound Remember : speed = distance v = d time t Data : Speed of sound in air = 340m/s 1. How far will sound travel in 5 seconds? 2. How long will it take sound to travel a distance of 200 m? 3. A flash of lightning is seen and the thunder is heard 3 s later. How far away did the electrical discharge causing the thunder and lightning take place? 4. A horn and a lamp are arranged so that they can be switched on together. A pupil sets up the horn and lamp at one end of a field and another pupil takes a stopwatch to the other end of the field 200 m away. The lamp and horn are switched on and the second pupil starts the stopwatch when the light is seen and stops it when the horn is heard. The reading on the stopwatch is 0.55 seconds. What value does this give for the speed of sound in air? 5. Two sound sensors are placed 60 cm apart and connected to a computer by an interface. When a sound reaches the first sensor a clock in the computer is switched on and when the sound reaches the second sensor the clock is switched off. When a sound is sent towards the sensor the clock gives a reading of s. What value does this experiment give for the speed of sound in air? 6. A plane goes through the sound barrier and the sonic boom is heard 12 s later by a person on the ground. How far away was the person from the plane? 7. A girl standing in front of a cliff claps her hands. She hears the echo 0.25 s later. If the distance between the girl and the cliff is 80 m, calculate the speed of sound in air. 8. A firework explodes at a height of 120 m above the ground. How long after seeing the explosion of the firework will the sound be heard? 9. At a school sports meeting the timekeepers are 100 m away from the starter. How long after seeing the smoke from the starter s gun will the timekeepers hear the bang from the gun? 1

2 10. The light from a lighthouse flashes at the same time as a foghorn is sounded. The sound is heard on a ship at sea 2.2 s after the light is seen. Calculate how far the ship is from the lighthouse. 11. During a journey to America Concorde flies at twice the speed of sound for one hour. How far does the plane travel in this time? 12. Describe an experiment which you could perform to measure the speed of sound in air, Your description should include : (i) (ii) (iii) a diagram of the apparatus you would use; the measurements you would take; how you would calculate your final result 13. At the start of a 400m race the athlete nearest to the starter is 5 m away while the athlete furthest away form the starter is 15 m away. Calculate the time between each of the athlete s hearing the starter s gun. 14. The speed of aeroplanes is sometimes given in Mach numbers where Mach 1 is the speed of sound. Calculate how long it will take a plane flying at Mach 3.5 to travel a distance of 1500 km. 2

3 Wavelength, Frequency and Amplitude of Waves 1. Answer the following questions about waves (a) What is the name given to the distance between two crests? (b) What is the distance between the centre of a wave and its crest called? (c) What name is given to the number of waves which pass a point in one second? (d) What is the distance between two troughs called? (e) What name is given to a wave where the material in which the wave is travelling moves at right angles to the direction of the wave? (f) What type of wave is a sound wave? (g) What is the distance between two compressions in a sound wave called? 2. The diagram below represents a wave travelling along a slinky spring (a) Which three different distances represent the wavelength of a wave? (b) Which distance represents the amplitude of the wave? 3. The diagram below represents a wave travelling from left to right. (a) Calculate the wavelength of the wave (b) What is the amplitude of the wave? 4. The diagram below shows water waves travelling over a pond. The distance between X and Y is 18 m and between P and Q is 0.5 m. Calculate : (a) the wavelength of the waves; (b) the amplitude of the waves; (c) the distance between X and P. 3

4 5. The waves in the diagram below have a wavelength of 1.5 m and an amplitude of 5 cm. Calculate the distance between: (a) P and Q (b) P and R (c) S and T (d) R and T 6. At swimming baths a child counts 16 waves passing her in 20 seconds. (a) What is the frequency of the waves? (b) How many waves would pass her in 5 seconds? 7. Water from a tap drips into a bath an produces waves on the surface of the water. The water from the tap is dripping at a rate of 40 drips every minute. (a) Calculate the frequency of the waves produced on the surface of the water. (b) What is the time between each drip falling into the bath? 8. A branch of a tree dips at a regular rate into a pond. The diagram below shows the waves spreading out over the surface of the pond. The lines drawn on the diagram represent crests and the spaces between them the troughs. The distance from the tree branch to point P is 4.5 m. (a) (b) (c) What is the wavelength of the waves? The crest at P took 2 seconds to travel out from the tree branch. Calculate the speed of the waves. The branch dips into the water at a rate of 90 times every minute. What is the frequency of the waves produced? 4

5 Water and Sound Waves 1. A child counts the number of waves passing the entrance to the harbour and finds that 15 waves pass in a time of 30 seconds. (a) What is the frequency of the waves entering the harbour? (b) How many waves would enter the harbour in 5 minutes? 2. The diagram below shows a water wave in a tank which is 12 m long. (a) What is the wavelength of the waves? (b) What is the amplitude of the waves? 3. The diagram below represents a wave of wavelength 1.5 m and amplitude 20 cm. What is the distance between (a) X and Y; (b) Y and Z? 4. Calculate the speed of a water wave moving across a pond if the wave has a frequency of 0.4 Hz and a wavelength of 2.5 m. 5. A girl sings a note of frequency 1000Hz. What is the wavelength of the sound? (Speed of sound in air = 340 m/s) 6. A light wave has a frequency of 5 x Hz. Calculate the wavelength of the light. (Speed of light in air = 3 x 10 8 m/s) 7. A wave machine, in a tank of water, produces 80 crests every minute, the distance between each crest being 0.6 m. Calculate : (a) the frequency of the waves; (b) the wavelength of the waves; (c) the speed of the waves. 5

6 8. A swimming pool is 50 m long. A wave machine produces waves of wavelength 2.5 m. The crest of a wave takes 20 seconds to travel from one end of the pool to the other. Calculate : (a) the speed of the waves in the pool; (b) the frequency of the waves produced. 9. The branch of a tree =, blowing in the wind, dips into a pond and produces a wave of frequency 0.2Hz. A wave takes 5.0 seconds to travel a distance of 20 m across the pond. Calculate : (a) the speed of the waves travelling across the pond; (b) the wavelength of the waves on the pond. 10. A loudspeaker vibrates times every minute. (a) What is the frequency of the sound produced? (b) Calculate the wavelength of the sound produced. (speed of sound in air = 340 m/s) 11. A speed boat travelling along a loch causes waves of wavelength 2.3 m and frequency 0.4 Hz to be produced. Calculate the speed of the waves produced by the boat. 12. In a film, a steam train blows its whistle and produces a note of frequency 1200 Hz. The whistle is heard at the station 1.25 seconds later. (a) What is the wavelength of the sound produced by the whistle? (b) How far from the station was the train when the whistle was blown? 13. The speed of sound in water is 1400m/s. A dolphin emits a squeak of frequency 1500 Hz. Calculate the wavelength of the sound in water. 14. A trawler, searching for fish, sends out a short burst of sound vertically through the seawater and receives an echo from a shoal of fish 0.5 seconds later. The sound has a frequency of 1800 Hz. Calculate (a) the depth of the shoal of fish; (b) the wavelength of the sound in seawater. (speed of sound in seawater = 1500 m/s) 6

7 Scientific Notation 1. Light travels at a speed of 3 x 108 m/s. Write this out in full. 2. The area of the Sahara desert is approximately 8.4 x 106 square kilometres. Write this out in full. 3. Ireland is the 20 large island in the world and covers an area of square miles. This number can be written as x 10n. What is the value of n. 4. Harvard, the richest university in the world, has endowments worth 259 million pounds in This number of pounds can be written as x 10n. What is the value of n. 5. The diameter of a sodium atom is millimetres. This number can be written as 3 x 10-n. Write down the value of n. 6. The distance between Neptune and the Sun is approximately miles. This can be written as x 10n. What is the value of n? square miles of the Earth s surface is covered by the sea. Write this down in scientific notation. 8. The units curies or becquerels can be used to measure radioactivity, where 1 curie = becquerels. After a nuclear accident, the radioactivity was estimated as 1 curie. Express this measurement in becquerels in scientific notation. 9. Loch Ness, home of the famous monster, has a volume of approximately cubic metres. Write this down in scientific notation. 10. The charge on one electron is coulombs. Express this value in scientific notation. 7

8 Radio Waves Data : Speed of radio waves in air = 3 x 10 8 m/s 1. How far will a radio wave travel in 5 seconds? 2. How long does it take a radio wave to travel a distance of m? 3. It takes a radio wave 8 minutes to travel from the Earth to the Sun. Calculate the distance between the Earth and the Sun. 4. Mission control at a space centre sends a message to an astronaut on the Moon. The distance between the Earth and the Moon is m. Calculate the shortest time it will take for mission control to receive back an answer from the astronaut. 5. Radio Clyde broadcasts on MHz. Calculate the wavelength of the radio frequency carrier wave used by Radio Clyde. 6. A radio station broadcasts using a carrier wave of wavelength 3.3 m. Calculate the frequency on which the station broadcasts. 7. Copy and complete the following table giving information about radio stations. You must show all your working. Radio Station Frequency Wavelength Radio Scotland Classic FM Radio 1 Clyde 2 Radio 4 LW 810 khz 98 MHz 198 khz 3 m 261 m 8

9 Television Data : Speed of radio waves in air = 3 x 10 8 m/s 1. Below is a block diagram with some of the parts omitted. Name the parts P, Q, R, S and T. Q Sound amplifier aerial P Vision decoder S R T 2. What do each of the following parts do in a TV receiver? (a) amplifier (b) electrical supply (c) aerial (d) vision decoder (e) loudspeaker (f) sound amplifier (g) tube 3. Name the three colours used to produce the picture on a colour TV screen. 4. Which colours are used to produce : (a)cyan (b) magenta (c) white (d) yellow? 5. Describe how one frame of a picture is built up on the screen of a TV? 6. How many electron guns are there in a colour TV? 7. Explain how the different frames built up on the screen every twenty-fifth of a second give rise to a moving picture. 8. How long does it take the radio wave carrying a TV signal to travel from London to Glasgow, a distance of 640 kilometres? 9. The carrier wave for BBC1 is broadcast at a frequency of MHz. What is the wavelength of the carrier wave? 10. The strip for the Brazilian football team is yellow. Electrons guns in the TV can fire electrons at areas of green, red or blue phosphorus on the screen and make them glow. (a) Which guns must be used when showing the Brazil strip? (b) Holland play in orange. What change would need to be made in the guns to show this strip? (c) Which guns would need to be firing to show England s white strip? 9

10 Transmission of Radio, Television and Microwaves 1 Data : Speed of radio waves in air = 3 x 10 8 m/s 1. How long does it take a radio wave to travel a distance of 40 km from Glasgow to Edinburgh? 2. A TV picture transmitted in Britain to a receiver in the USA takes a time of seconds. Calculate the distance between the transmitter and the receiver. 3. A mobile phone uses microwaves to carry a message from a caller to a second mobile phone a distance of 500 km away. How long does it take the message to travel between the phones? 4. A transatlantic telephone call is sent via satellite. The satellite is positioned a distance of km between the transmitter and receiver as shown below. satellite 4200 km 4200 km Receiver Transmitter Microwaves are used to send the telephone message to and from the satellite. Calculate how long it takes the call to travel between the transmitter and receiver. 5. When astronauts visited the Moon in 1969 they communicated with the ground control on Earth by radio waves. Calculate the least time it would take someone in ground control to receive back an answer to a question which they asked the astronauts. (Distance between the Earth and the Moon = 3.84 x 10 5 km) 6. A distant star explodes and radio waves are given out. It takes 10 years for the radio waves to reach the Earth. Calculate how far away the star was from the Earth. 10

11 Transmission of Radio, Television and Microwaves 2 Data : Speed of radio waves in air = 3 x 10 8 m/s 1. Calculate the wavelength of Channel 4 which broadcasts on a frequency of MHz. 2. An amateur radio enthusiast sends her radio messages using a wavelength of 80 m. Calculate the frequency at which the waves are transmitted. 3. Microwaves of frequency 5.5 GHz are used to carry telephone messages to a satellite. Calculate the wavelength of the microwaves. 4. The pilot of a plane communicates with the controller at an airport using radio waves of wavelength 0.8 m. Calculate the frequency of the waves being used by the pilot. 5. Ultra High Frequency (or UHF) uses radio waves in the range 300 MHz to 3000 MHz. Calculate the maximum and minimum wavelengths of the radio waves used in the UHF frequency band. 11

12 Satellites and Dish Aerials Read Essential Physics for S-Grade, Section 5, pages and then answer the following questions in sentences. 1. What is the time taken for a satellite to complete one orbit called? 2. What does the time taken for the satellite to complete one orbit depend on? 3. What is meant by a geostationary satellite? 4. Describe how a telephone message could be sent from Britain to America using a satellite. 5. Using a diagram describe how a dish aerial is able to increase the strength of an incoming signal at the aerial detector. 12

S3 Physics. Paisley Grammar School Physics Department UNIT 1. Signals PUPIL PACK. Name: Class: Teacher:

S3 Physics. Paisley Grammar School Physics Department UNIT 1. Signals PUPIL PACK. Name: Class: Teacher: Name: Class: Teacher: Paisley Grammar School Physics Department S3 Physics UNIT 1 Signals PUPIL PACK Study Guides Summary Notes Questions Homework Sheets S3 Physics: Signals Study Guide Section 1 Communication