Andy,

Second question first!

Have you come across the equation d = vt (distance = velocity multiplied by time)?

If you have it is fairly straightforward to work out how far a light year is in metres.

One light year is the distance light travels in one year. I would imagine that you have been given the speed of light, which is 3*10^8m/s.

This means that you have a speed (the speed of light) and a time (one year, you need to convert this into seconds though as the speed of light is given n meters per second). Given this information, and the equation d = vt, you should be easily able to work out the distance in metres. Does that make sense?

As for the first question. you are given a variety of options in light-units.

1 light second means that it takes 1 second for light from the sun to reach the earth; 1 light minute means that it takes light 1 minute to reach the earth; and so on.

What you need to work out is how long light reaches to get from the sun to the earth.

You need the speed of light again (given above) and the distance between the sun and the earth in metres (which an internet search suggests is 1.49476*10^11m). You therefore have a distance and a speed, so you can workout the time by rearranging v=dt and substituting in the numbers.

Does all this make sense? Feel free to ask any questions if it doesn't!

Gordon