Physics Important

Calculation for average orbital speed

2 pie radius/ time

formation process of stable stars

Nebula cloud collapse due to gravity

Spin faster

Protostar formed by accretion and hydrogen temperature increase

Stable star when nuclear fusion starts and inward force, gravitational force, equals to outward force, heat.

Value for 1 light year

9.5 × 10 power 15 m

Process to end of small stable star

Hydrogen runs out

Expand to be red giant

Outer layers have weak attraction to center is blown off in ring and forms planetary nebula

Core left behind forming white dwarf star

Process to end of large stable stars

Hydrogen runs out

Expands into red supergiant

Its force outward, heat, outweighs inward force causing explosion

Supernova

Nebula forms

Form neutron star or blackhole

Value for hubble constant

2.2 × 10 power -18

How to calculate age of universe

1/ Hubble constant

How wavelength affects diffraction at edge

Longer wavelength = more diffraction

Shorter wavelength = less diffraction

Range of normal human hearing

20Hz to 20000Hz

Equation for speed in freefall

½ gt sq

What is nucleons

any particle in nucleus of atom: proton and neutron

Purpose of electromagnetic spectrum

Radio, Tv broadcasting

Satellite signals

Remote control, thermal imaging

Sterillisation, bank note check

Medical imaging, airport security

Killing cancer cells, sterilise equipment

What can be deduced from redshift and brightness of supernova

By redshift- speed of galaxy moving away from us

By brightness of supernova- distance galaxy is from us

An electrical device has a metal case explain the benefit of earthing the metal case.

Prevents electrocution/ metal case cant be live

If live wire touches metal case

explain and describe what can be deduced cosmic microwave background radiation

microwave radiation is observed at all points in space around the Earth

radiation was produced when Universe was formed

radiation has expanded into the microwave region of the electromagnetic spectrum

evidence that universe expanded

Describe how the four innermost planets of Solar System were formed

dust and gas orbit sun

contain many different elements

rotation of materials around sun

particles accrete

forming large rocks

because of gravitational attraction

material move to form protoplanetary disk orbiting sun

formation of planetary core

in solenoid when does direction of current reverse

same entry, different pole

different entry, same pole

what happens in smoke detector

alpha particles used to ionised air

smoke particles absorb/ block alpha particles

interrupt current

alarm triggers

Can speed be negative?

Speed always positive

velocity can be negative

define gravitational field strength

gravitational fuel strength per unit mass on an object in a gravitational field

advantages of using optical fibre to transmit data

faster data transmission

carry large amounts of data

secure

little data/ signal loss

What is critical angle

angle of incidence at which the angle of refraction is exactly 90 degrees

precautions that you would take to obtain accurate readings in the focal lens experiment

Use darken room/brighter object

move lens slowly back and forth to find sharpest image

Mark the centre of the lens on its holder

ensure the object lens and screen are vertical