There’s a new TV series coming up very soon, made by Professor Brian Cox. It’s called “Wonders of the Solar System” and begins on BBC2 next Sunday, 7th March 2010, at 9 p.m. In it, Professor Cox ventures to some of the most extreme locations on Earth – including the tallest mountain, the bottom of the Pacific Ocean and the world’s driest desert – to paint a dazzling picture of a Solar System we are only now beginning to understand. Not to be missed!
Post script: there’s a children’s version of this series called “Space Hoppers”. It is being shown, also on BBC2, starting on Tuesday 9 March at 7:30 in the morning. More information here.
Today is the anniversary of the Queen’s accession to the throne and there was a 21-gun salute from Edinburgh Castle to mark the occasion. You can see part of last year’s taken by video on the castle on YouTube. I happened to be down on Princes Street today, and caught a couple of the shots on video. Physics students should be able explain why you see the smoke from the cannon before you hear the bang. If the speed of light is 300 thousand kilometres per second and the speed of sound in air is 340 metres per second, can you work out how far away I was from the cannon?
This tutorial shows how to draw the ray diagrams for a convex lens for the three important cases: (i) an object placed further than 2x focal length from the lens, (ii) an object placed between 1x and 2x focal length from the lens and (iii) an object placed less than 1x focal length from the lens.
You will see how in each case, the image is (i) real and inverted, (ii) out of focus and (iii) virtual, upright and magnified.
Try to construct the diagrams yourself, remembering the three construction lines from the top of the object parallel to the optical axis, through the centre of the lens and through the focal point.
