P3 Essential Questions X Rays, CT Scans and Ultrasound

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P3 Essential Questions X Rays, CT Scans and Ultrasound Ultrasound and X-rays are waves used in hospitals to create images of the inside of the human body.

1 P3 Essential Questions X Rays, CT Scans and Ultrasound Ultrasound and X-rays are waves used in hospitals to create images of the inside of the human body. To produce the images below, the waves must enter the human body. Ultrasound scan of an unborn child X-ray of a broken bone Describe the features of ultrasound and X-rays, and what happens to each type of wave after it has entered the human body. It would not be safe to use X-rays to produce an image of an unborn child. Explain why. (6) Explain fully why pregnant women should not normally have X-rays of the lower body. Before switching on the X-ray machine, the radiographer goes behind a screen. Explain why the radiographer does this. (4) Page 1

What is ultrasound?... Ultrasound can be used for medical treatments as well as for imaging.

Ultrasound can be used to measure the depth of water below a ship.

80 seconds for the emitted ultrasound to be received back at the ship.

Speed of ultrasound in water = 1600 m / s Use the correct equation from the Physics

.. metres The diagram shows four sound waves, J, K, L and M, represented on an oscilloscope

2 What is ultrasound?... Ultrasound can be used for medical treatments as well as for imaging. Give one use of ultrasound for medical treatment. Ultrasound can be used to measure the depth of water below a ship. A pulse of ultrasound is sent out from an electronic system on-board the ship. It takes 0.80 seconds for the emitted ultrasound to be received back at the ship. Calculate the depth of the water. Speed of ultrasound in water = 1600 m / s Use the correct equation from the Physics Equations Sheet. Depth of water =... metres The diagram shows four sound waves, J, K, L and M, represented on an oscilloscope screen. They are all drawn to the same scale. J K L M Which two of the waves have the same amplitude? Wave... and wave... Which of the waves would sound the loudest? Wave... Only one of the waves is an ultrasound wave. Which one is the ultrasound wave? Wave... Give a reason for your answer.... Page 2

3 State one advantage and one disadvantage of using a CT scanner, compared with ultrasound scanning, for forming images of the inside of the human body. Advantage of CT scanning... Disadvantage of CT scanning... Explain the advantage of a CT scan compared to an X-ray. The Eye (a) The diagram shows a section through a human eye. Use words from the box to label the diagram. Ciliary muscle Cornea Iris Lens Pupil Retina Each part of the human eye has a function. Complete the table below. Part of the human eye Function of the part... Changes size to make sure the correct amount of light enters the eye. Ciliary muscles Lens Page 3

Figure 2 shows light rays travelling into the human eye. Give the name of the defect of vision shown in Figure 2.

4 Figure 2 shows light rays travelling into the human eye. Give the name of the defect of vision shown in Figure A concave (diverging) lens can be used to correct the defect of vision shown in Figure 2. Complete the ray diagram in Figure 3 to show how a concave lens produces an image of the object. Use an arrow to represent the image. It is important that muscles can change the power of the lens in the eye. State why. Page 4

.. The diagram shows a converging lens being used as a magnifying glass.

5 Lenses A camera contains a convex (converging) lens. Complete the ray diagram to show how the lens produces an image of the object. State two words to describe the nature of the image produced by the lens in the camera. F = Principal focus (4) The diagram shows a converging lens being used as a magnifying glass. On the diagram, use a ruler to draw two rays from the top of the object which show how and where the image is formed. Represent the image by an arrow drawn at the correct position. Use the equation in the box to calculate the magnification produced by the lens. Page 5

6 Show clearly how you work out your answer. A camera also uses a converging lens to form an image. Magnification =... Describe how the image formed by the lens in a camera is different from the image formed by a lens used as a magnifying glass. The focal length of a diverging lens is 5 cm. A student looking through the lens sees the image of a pin. Complete the ray diagram below to show how the image of the pin is formed. The lens can be used in a camera to produce a real image. Explain why a real image must be produced in a camera and how the object and the lens are positioned to produce a real image which is smaller than the object. Do not draw a ray diagram as part of your answer. Page 6

$Refraction Figure 1 shows a ray of light travelling through a semicircular glass block. The angle of incidence is labelled i. The angle of incidence i equals the critical angle for the glass.$ $.. Figure 2 shows what happens to a ray of light as it meets the boundary between air and water. The refractive index of the water is 1.3. Calculate the angle of refraction r................ Angle of refraction =.$

7 Refraction Figure 1 shows a ray of light travelling through a semicircular glass block. The angle of incidence is labelled i. The angle of incidence i equals the critical angle for the glass. Complete Figure 1 to show what happens to the ray of light at the glass-to-air boundary. The critical angle for the glass is 41. Calculate the refractive index of the glass Refractive index =... Figure 2 shows what happens to a ray of light as it meets the boundary between air and water. The refractive index of the water is 1.3. Calculate the angle of refraction r Angle of refraction =... degrees Figure 3 shows how a ray of light from a laser travels along an optical fibre. Why does the ray of light stay within the optical fibre? The material used to make the optical fibre has a refractive index of Calculate the critical angle of this material. Critical angle =... degrees Page 7

8 Centre of Mass and Moments Complete the sentence. The moment of a force is the... effect of the force. What is meant by the centre of mass of an object?... Some children build a see-saw using a plank of wood and a pivot. The centre of mass of the plank is above the pivot. Figure 1 shows a boy sitting on the see-saw. His weight is 400 N. Calculate the anticlockwise moment of the boy in Nm Nm Figure 2 shows a girl sitting at the opposite end of the see-saw. Her weight is 300 N. The see-saw is now balanced. The children move the plank. Its centre of mass, M, is now 0.25 m from the pivot as shown in Figure 3. The boy and girl sit on the see-saw as shown in Figure 3. Describe and explain the rotation of the see-saw. The boy gets off the see-saw and a bigger boy gets on it in the same place. The girl stays in the position shown in Figure 3. The plank is balanced. The weight of the plank is 270 N. Calculate the weight of the bigger boy. Weight of the bigger boy =... N Page 8

The diagram shows a man standing in an airport queue with his wheeled bag. The man applies an upward force to the handle of his bag to stop the bag from falling.

9 The diagram shows a man standing in an airport queue with his wheeled bag. The man applies an upward force to the handle of his bag to stop the bag from falling. The moment of this force about the pivot is 36 Nm. Calculate the upward force the man applies to the handle of his bag. Force =... N When the man lets go of the bag handle, the bag falls and hits the floor. Explain why. Suggest two ways the wheeled bag could be made more stable: During his holiday the man visits the Foucault Pendulum in Paris, France. The pendulum makes 10 complete swings every 160 seconds. Calculate the frequency of the pendulum and give the unit. Frequency =... Page 9

Hydraulics Musicians sometimes perform on a moving platform. Figure 1 shows the parts of the lifting machine used to move the platform up and down.

10 Hydraulics Musicians sometimes perform on a moving platform. Figure 1 shows the parts of the lifting machine used to move the platform up and down. What type of system uses a liquid to transmit a force?... The pump creates a pressure in the liquid of 8.75 x 10 4 Pa to move the platform upwards. Calculate the force that the liquid applies to the piston. A man uses a car jack to lift his car. Figure 3 shows a simple diagram of a car jack. The man pushes down with an effort force. Force =... N This results in a much larger force acting upwards on the car. Use information from Figure 3 to explain how. (4) Page 10

11 Circular Motion The fairground ride called The Rotor is a large cylinder which rotates. When the cylinder reaches its maximum speed the floor drops away and the riders inside the cylinder are left against the cylinder wall. Explain how the cylinder is rotating at a constant speed but at the same time the riders inside the cylinder are accelerating In which direction do the riders accelerate? What name is given to the resultant force that causes the riders to accelerate? At the end of the ride the floor goes back into place and the cylinder slows down and stops. How does the resultant force on the riders change as the cylinder slows down? The London Eye is one of the largest observation wheels in the world. The passengers ride in capsules. Each capsule moves in a circular path and accelerates. The designers of the London Eye had to consider three factors which affect the resultant force described in part (b). Name three factors that affect the resultant force. A satellite in stable Earth orbit moves at a constant speed in a circular orbit because there is a single force acting on it. Explain why the kinetic energy of the satellite remains constant. Page 11

12 Transformers Transformers are used to change potential differences (p.d.) in the National Grid. Figure 1 shows a step-up transformer that is used at a power station. Use words from the box to label Figure 1 Input p.d. Primary coil Secondary coil Iron core Output p.d (4) Explain how a transformer works. One of the coils in Figure 1 has a p.d. of 25 kv across it and has 1000 turns. The other coil has a p.d. of 400 kv across it. Calculate the number of turns on this other coil. (5) Number of turns =... An 18 V battery could not be used as the input of a transformer. Explain why. The coils of a transformer are made of insulated wire. Why is this insulation necessary? Why is the core made of iron?... Page 12

13 Explain why a step-up transformer is used at a power station. The Motor Effect A laboratory technician sets up a demonstration. A flexible wire is suspended between the ends of a horseshoe magnet. The flexible wire hangs from a cotton thread. When the switch is closed, the wire kicks forward. Identify the effect which is being demonstrated.... A teacher makes some changes to the set-up of the demonstration. What effect, if any, will each of the following changes have? - more powerful horseshoe magnet is used. - The connections to the power supply are reversed. A mobile phone charger contains a step-down transformer. A switch mode transformer is used rather than a traditional transformer. Describe the advantages of using a switch mode transformer in the charger rather than a traditional transformer. Page 13

used to diagnose and treat medical conditions. State the precautions necessary when X ray machines and CT scanners are used.

Page 1 State the properties of X rays. Describe how X rays can be used to diagnose and treat medical conditions. State the precautions necessary when X ray machines and CT scanners are used. What is meant