Explain

Question 1

Explain the use of charge particles in the magnetic and electric fields of a mass spectrometer

Answer 1

Depending on E and B strength
The mass of charged particles detected can be changed
Smaller E, larger mass particles detected and vice versa

Question 2

Explain the effect of a uniform electric field on the motion of a charged particle

Answer 2

If E is uniform
Acceleration of charged particle is constant
If particle positive then acceleration direction of field and vice versa

Question 3

Explain how soft tissues like the intestines can be images using barium meal

Answer 3

Contrast media used to make soft tissues more visible
Barium absorbs X-Rays
Barium coats the walls enabling outlines to be seen on X-Rays

Question 4

Explain what is meant by the Doppler effect

Answer 4

A change in frequency and wavelength of a wave

Caused by change in distance between object creating the wave and the object measuring the wave

Question 5

Explain qualitatively how the Doppler effect can be used to determine the speed of blood

Answer 5

Uses ultrasound waves
Sound waves reflected by moving blood cells
Change in frequency/wavelength enables speed of blood to be founded

Question 6

Explain how ultrasound transducers emit and receive high frequency sound

Answer 6

Transducer converts one form of energy to another (in this case electrical energy into ultrasound energy by piezo-electric material such as Quartz)

Question 7

Explain that the standard model of the universe implies a finite age for the universe (the Big Bang)

Answer 7

• galaxies moving apart/universe is expanding
• if galaxies have always been moving apart then the must have been closer together or started from a point
• evidence in red shift in optical/microwave
• further away the galaxy the faster the speed of recession
• the existence of 2.7K microwave background radiation levels

Question 8

Explain that the universe can be open flat or closed

Answer 8

Open: universe expands for all time
Flat: Expands to a limit (but never reaches it)
Closed: universe collapses back

Question 9

Explain that the ultimate fate of the universe depends on its density

Answer 9

If av. p of universe critical p = closed

Av. P = or close to critical p. = flat

Question 10

Explain that it is currently believed that the density of the universe is close to critical density needed for a flat universe

Answer 10

p0 equation (form book) estimates value less than critical
But rotation of galaxies show they have more mass than we can see and the inflationary expansion theory suggests that density = critical