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Physics Unit 3 - 3A
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Questions in this quiz (13)
1What are X-rays? Name two materials X-rays are absorbed by.
- AAn X-ray is a high frequency, short wavelength electromagnetic wave. X-rays are absorbed by dense materials like bones and metals.
- BBlah.
2What is a 'charge-coupled device'? What is it used for?
- AA silicon chip that is divided into millions of identical pixels. It detects X-rays and produces electronic signals which are used to form high resolution images.
- BBlah.
3How do CT scans form images of the body?
- AThe patient is put inside the cylindrical scanner, and an X-ray beam is fired through the body from an X-ray tube and picked up by detectors on the opposite side. The X-ray tube and detectors rotated during the scan.
A computer interprets the signals from the detectors to form an image of a two-dimensional slice through the body. - BBlah.
- AThe patient is put inside the cylindrical scanner, and an X-ray beam is fired through the body from an X-ray tube and picked up by detectors on the opposite side. The X-ray tube and detectors rotated during the scan.
4Describe how X-rays can be used to treat cancer.
- AX-rays can be used because they cause ionization - they kill living cells. X-rays can therefore be used to kill cancerous cells.
- BBlah.
5Describe how X-rays can be used to treat cancer.
- AX-rays can be used because they cause ionization - they kill living cells. X-rays can therefore be used to kill cancerous cells.
- BBlah.
6What precautions can radiographers take to minimize their radiation dose?
- AWear a lead apron, stand behind a lead screen, or leave the room whilst the scan takes place.
- BBlah.
7What is ultrasound?
- AUltrasound is sound with a higher frequency than we can hear.
- BBlah.
8Ultrasound travels through fat at a velocity of 1000 m/s. A pulse of Ultrasound is sent into a person and is partially reflected off a layer of fat and a layer of muscle. The time between two reflected pulses of ultrasound is 0.00004 s. How thick is the layer of fat?
- AS = V x T
1000 x 0.00004 = 0.04
0.04 / 2 = 0.02m = 2 cm - BBlah.
- AS = V x T
9Explain why Ultrasound rather than X-rays are used to take images of a fetus.
- AX-rays can cause cancer in high doses due to the ionisation. Ultrasound are non-ionising.
- BBlah.
10What are the advantages of using CT scans over ultrasound scans?
- ACT scans provide a much more detailed, high resolution image and can be used to diagnose much more complicated illnesses and are often used in the planning of surgery.. Ultrasound images usually come out fuzzy.
- BBlah.
11What is Refraction?
- ARefraction is when waves change direction as they enter a new medium.
- BBlah.
12What is the formula for refractive index?
- An = sin i
-----
sin r - Bblah.
- An = sin i
13Calculate the refractive index of a block of clear plastic if a beam of light enters it with an angle of incidence of 27 degrees and is refracted at an angle of 18 degrees.
- Asin 27 / sin 18 = 0.45 / 0.31 = 1.45
- Bblah.
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- Quiz on Physics Unit 3 - 3A, created by Libby Shaw on 22/05/2013.
- Author
- Libby Shaw
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- English
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