P3- Physics

Question 1

What are x rays? Name two materials X-rays are absorbed by?

Answer 1

X-rays are high frequency short wavelength em waves. Absorbed by dense materials like bones and metal

Question 2

What is a charged couple device?

Answer 2

Small silicon chips they detect x rays and produce electronic Signals which form high resolution images

Question 3

How do CT scans form images of the body?

Answer 3

Use X-rays to pricey high resolution images of soft and hard tissue.

Question 4

How can X-rays be used to treat cancer?

Answer 4

X-rays can cause ionisation which will kill living cells the right dosage is needed to kill the cancer cells and not many normal cells

Question 5

What precautions can radiographer take to minimise radiation dose?

Answer 5

Wear lead aprons, stand behind a lead screen or leave the room whilst the scan is being done

Question 6

What is ultrasound?

Answer 6

Is sound with a frequency above 20 thousand hertz

Question 7

Why use ultrasound rather than X-rays when taking an image of the fetus?

Answer 7

When an ultrasound reaches the boundary of two different materials some of the wave is reflected back and detected which is processed by a computer

Question 8

Why might people say ultrasound is better than ct scans

Answer 8

Ultrasound is non ionising so is safe, CT scans use X-rays which are ionising and can cause cancer.

Question 9

What is refraction ?

Answer 9

Refraction is when waves change direction as they enter a different medium, caused by a change in density from one medium to another which changes speed of the waves

Question 10

What is the principal focus of a lens ?

Answer 10

There is a principal focus on each side of the lens. The distance from the centre of lens to the principal focus is called the vocal length

Question 11

What type of lenses are used for magnifying glasses?

Answer 11

Use converging lenses and is a virtual image

Question 12

What two things affect the focal length of a lens?

Answer 12

The power of the lens and distance to the lens

Question 13

What is the near point for Vision?

Answer 13

For adults is 25cm

Question 14

What is the far point of vision?

Answer 14

Infinity for humans

Question 15

Two reasons for near point vision?

Answer 15

It’s power increases, the lens changes shape and the focal length decreases. But the distance between the lens and the image stays the same

Question 16

How can lasers be used to correct vision problems?

Answer 16

Laser is used to vaporise some of the cornea to change its shape

Question 17

What is total internal reflection?

Answer 17

When a wave travels through a dense substance towards a less dense substance

Question 18

What happens if the angel of incidence is less than the critical island ?

Answer 18

Most of light is passed out with a bit being internally reflected

Question 19

What happens if the angle of incidence is greater than the critical angle?

Answer 19

No light comes out all is internally reflected

Question 20

What is an endoscope ?

Answer 20

Thin tube containing optical fibres that lets surgeons examine inside the body