A video on total internal reflection

What is a tangent to circle?

Tangent to a circle: A line that contacts an arc or circle at only one point.
Tangent line is always at right angles to the radius at the point of contact.

Check this out for an interactive experience with a tangent to a circle.

We were talking about tangent to a circle in 3H on 27 January 2015, when discussing the total internal reflection in a semi-circular glass block.

Does diamond conduct electricity?

The answer is no. Diamond is hard and has high melting point, but it does not conduct electricity as there are no free electrons in diamond.

Read up more about the properties of diamond here.

This question was raised by 1B on 21 January 2015 in the chemistry lab.

Vernier calipers simulator

Go to this link and scroll down to the simulator that looks like this:

Please take note that  while the main scale is in centimetres, the reading shown is in millimetres. Therefore, the reading of the measurement shown above is 0.75 cm or 7.5 mm.

Micrometer simulator

Click on the diagram below to go to a simulation on micrometer screw gauge.

Uses of electrostatics

Photocopying and laser printing are just some of the uses of electrostatics. 

See more uses at this BBC link.