Re-sit papers

If you are re-sitting the year 10 modules on Monday 23 June, here's a link to get you the past papers that you need. There are mark schemes too.

http://www.aqa.org.uk/qual/gcse/newscience/extassessover.php

Star formation

Satellites

A geostationary orbit is one above the equator. It takes the satellite 24 hours to go round once. This means that satellite Y is always above town A. (Note that the satellite doesn't stay still. It does move but so does town A. They stay fixed relative to each other.)

• Used for communications eg phone and TV
• Because the satellite is in a fixed position relative to the Earth so dishes can always point in the same direction.
• GPS satellites are geostationary too.
• You SatNav constantly checks where it is in relation to these satellites.

Polar orbit goes over the poles and covers a lot of territory.

• Many countries visited so good for spying.
• Close to the ground so better photos (GoogleEarth)
• Weather photos

Ultrasound

Think about what happens when light hits a window. Some of it goes through and some is reflected. You can choose to focus on what is reflected or on what is on the other side of the window. We call this partial reflection.

In the same way, ultrasound is partially reflected when it goes from one medium into another medium. The ultrasound changes speed when it goes from one medium to another. The bigger the change in speed, the more is reflected. It is the reflection that allows us to make up a picture using ultrasound scanning for eg foetuses.

There is a big change in speed between air and muscle, so if you fire ultrasound towards a woman's stomach, it would mostly reflect and not get into her. For this reason, they smear saline gel on first because there is less of a reflection between saline gel and muscle.