Topic 9 - Applications of Waves and Radiation (GCSE Edexcel Physics Retrieval Questions)

What are the two types of lenses?

Convex/Converging and Concave/Diverging

Define focal length.

The distance from the lens to the principle focus.

How can you increase the power of a lens?

Decrease the focal length by curving the lens more.

What is a real image?

An image that is formed when the light rays from an object converge and meet each other and can be projected onto a screen

What is a virtual image?

An image that is formed when the light rays from an object do not meet but appear to meet behind the lens and cannot be projected onto a screen

What type of waves are sound waves?

Longitudinal

How does sound travel in air?

There are areas where the pressure of the air varies with the wave - compressions and rarefactions

Describe the relationship between the speed of sound in gas vs solids?

Sound travels faster in solids.

What is the range of frequencies that humans can hear?

20-20,000Hz

How does the human ear work to hear sound?

The pressure variations created by the sound wave exert a varying force on the eardrum causing it to vibrate. The small bones amplify the sound and the cochlea's tiny hairs create electrical impulses.

Define ultrasound.

Sound waves with a frequency above the human hearing range of 20 000 Hz

State two uses of ultrasound.

Foetal scanning and sonar.

How to ultrasound waves in foetal scanning distinguish boundaries?

The ultrasound waves are partially reflected back to the transducer by different boundaries, depending on the density of the tissue at the boundary.

How do you calculate the distance between a submarine and the sea floor using sonar?

2 x distance = speed/time

Define infrasound.

Sound waves with a frequency below the human hearing range of 20 Hz

Are P-Waves transverse or longitudinal?

Longitudinal

Are S-Waves transverse or longitudinal?

Transverse

Are P-Waves or S-Waves faster?

P-Waves

How do P-Waves give evidence for the structure of the earth?

They refract by different amounts at different boundaries.

How do S-Waves give evidence for the structure of the earth?

S-Waves can only travel through solids.

What evidence do P and S Waves give about the structure of the earth and why?

S-Waves - Mantle is solid, outer core is liquid. P-Wave refraction - inner core is solid.

Describe thermal equilibrium.

An object will reach a point of constant temperature where it is absorbing radiation at the same rate as it is emitting radiation

When will an object get hotter?

The temperature of a body increases when the body absorbs radiation faster than it emits radiation.

What is a perfect black body object?

A perfect black body is an object that absorbs all of the radiation that it comes in contact with. This means that it does not transmit or reflect any radiation.

Which colour is a better emitter of radiation - black or silver?

Black

Which colour is a better reflector of radiation - black or silver?

Silver