3a

Question 1

Name three ways X-rays are used in medicine?

Answer 1

Medical diagnosis, CT scans, treat cancer

Question 2

What are X-rays?

Answer 2

High frequency, short wavelength EM waves

Question 3

How can X-rays treat cancer?

Answer 3

The X-rays are focused on the tumour using a wide beam, this beam is rotated around the patient, this minimises the exposure of normal cells to radiation, and so reduces the chances of damaging the rest of the body.

Question 4

What is Ultrasound?

Answer 4

Ultrasound is sound with a higher frequency than we can hear

Question 5

Do Ultrasound waves get reflected at a boundary between media?

Answer 5

Partially

Question 6

What can you use to find boundaries?

Answer 6

Oscilloscope

Question 7

What formula can you use to work out the distance between the boundaries?

Answer 7

S = V X T 
s= distance in metres, m
v= speed in metres per second, m/s
t= time in seconds, s

Question 8

What are some uses of ultrasound?

Answer 8

Medicine— breaking down kidney stones, pre-natal scanning of a fetus

Question 9

What is refraction caused by?

Answer 9

The waves changing speed

Question 10

What is a refractive index?

Answer 10

The ratio of speed of light in a vacuum to see of light in that medium

Question 11

How do you work out the refractive index?

Answer 11

sin incident ray/ sin refracted ray

Question 12

What is a converging lens?

Answer 12

A converging lens is convex- it bulges outwards. It causes parallel rays of light to converge (move together) at the principal focus

Question 13

What is a diverging lens?

Answer 13

A diverging lens is concave- it caves inwards. It causes parallel rays of light to diverge (spread out)

Question 14

What is the axis of a lens?

Answer 14

A line passing through the middle of the lens

Question 15

Where is the principal focus of a converging lens?

Answer 15

Where rays hitting the lens parallel to the axis all meet

Question 16

Where is the principal focus of a diverging lens?

Answer 16

Point where rays hitting the lens parallel to the axis appear to come from

Question 17

DIVERGENT?

Answer 17

THEO JAMES

Question 18

What is focal length?

Answer 18

The distance from the centre of the lens to the principal focus

Question 19

What is a real image?

Answer 19

Where the light from an object comes together to form an image on a ‘screen’- like the image formed on an eyes retina

Question 20

What is a virtual image?

Answer 20

When the rays are diverging, so the light from the object appears to be coming from a completely different place

Question 21

What three things do you need to mention to describe an image properly?

Answer 21

1) How big it is compared to the object
2) Whether its upright or inverted relative to the object
3) Whether its real or virtual

Question 22

What type of image does a diverging lens always produce?

Answer 22

A virtual image

Question 23

What type of lens does a magnifying glass use?

Answer 23

Converging lens (magnified virtual image)

Question 24

What is the magnification formula?

Answer 24

Magnification= image height / object height

Question 25

The more powerful the lens, the more what it converges rays of light and therefore the what the focal length?

Answer 25

Strongly, shorter

Question 26

What formula do you need to work out the power of a lens?

Answer 26

Power(D) = 1/ Focal length

Question 27

What two factors is the focal length of a lens determined by?

Answer 27

The refractive index of the lens material, the curvature of the two surfaces of the lens

Question 28

What happens to the power of the lens if the curve becomes more strong?

Answer 28

The lens is more powerful

Question 29

What is the cornea?

Answer 29

A transparent window with a convex shape and a high refractive index. The cornea does most of the eye’s focusing

Question 30

What is the iris?

Answer 30

The coloured part of the eye. Controls the size of the pupil and therefore the intensity of light that enters the eye

Question 31

What is the role of the lens (in an eye)?

Answer 31

Focuses light from objects at varying distances

Question 32

What is the image formed on in the eye?

Answer 32

The retina

Question 33

How does a camera form images in a similar way to the eye?

Answer 33

The image on the film is a real image because light rays actually meet there. The image is smaller that the object, because the objects a lot further way than the focal length of the lens. Film in camera is equiv to the retina in our eye

Question 34

Name two causes of short sight

Answer 34

Long eyeball, too powerful cornea or lens

Question 35

Name two causes of long sight

Answer 35

Short eyeball, too weak cornea or lens

Question 36

What kind of lens can short sight be corrected with?

Answer 36

Diverging- diverges the light before it enters the eye which means the lens can focus it on the retina

Question 37

What kind of lens can long sight be corrected with?

Answer 37

Converging- the light is refracted and starts to converge before it enters the eye which means the lens can focus it on the retina

Question 38

How can lasers be used in surgery?

Answer 38

To vaporise some of the cornea to change its shape- this changes its focusing ability, can increase or decrease the power of the cornea so that the eye can focus images properly on the retina

Question 39

How can light be sent along optical fibres?

Answer 39

Total internal refraction

Question 40

If a wave travels through a dense substance like glass or water towards a less dense substance like air, can total internal refraction take place?

Answer 40

Indeedydoody

Question 41

Name two materials X-rays are absorbed by

Answer 41

Bones and metal

Question 42

What is a charge-coupled device?

Answer 42

A device that detects X-rays ad produces electronic signals which are used to form high resolution images

Question 43

Explain why ultrasound rather than X-rays are used to take images of a foetus

Answer 43

X-rays are ionising and therefore can cause cancer, not safe to use on babies

Question 44

What is the critical angle?

Answer 44

The smallest angle of incidence for which light is totally reflected

Question 45

A dense material with a high refractive index has a what critical angle?

Answer 45

A low critical angle

Question 46

What formula relates refractive index and critical angle (c)?

Answer 46

Refractive Index= 1/ sin c

Question 47

What is an endoscope?

Answer 47

A thin tube containing optical fibres that lets surgeons examine inside the body