What is refraction and why does it happen?Refraction refers to the bending of light as it travels from one medium to another. As light approaches the glass block from the left, it usually splits in two - some of it reflects off the surface, and some of it keeps going through The light that goes through bends at the surface. The angle that it bends at depends on what the two media are. For example, light will bend a different amount when it goesfrom air into glass than it does when it goes from air into water.the law of reflection states that angle of incidence (i) = angle of reflection (r), and it is evidentthat the incident ray and reflected ray have the same angle to the normal, which is a straightline perpendicular to the surface of the glass block.reflection happens why light bounces off an object too, and that enables us to see things! During refraction, light bends towards the normal That means that the angle of refraction of the refracted ray is smaller than the angle of incidence.Why does light enters the glass without being refracted?Because the incident ray is perpendicular to the surfaceAlso, note that the emergent ray bends away from the normal.MirrorsA concave mirror has a surface that bulges inwards.Images from a concave mirror are inverted and real (see video)http://www.physicsclassroom.com/mmedia/optics/rdcmc.cfmA real image refers to an image that come is produced from light that actually came from theobject.On the other hand a virtual image forms in places where light cannot reach and thereforecannot come from the object itself.But when the object is really close, the image formed is upright, magnified and virtual
A concave mirror can also be used to focus sunlight for heating purposes in addition to theones listed in your textbook.(Video: http://www.physicsclassroom.com/class/refln/u13l3a.cfm)Convex mirrorA convex mirror is quite the opposite of a concave mirror, its surface bulges outwards. A convex mirror causes light rays to diverge whereas a concave mirror causes light rays to converge.The result is that are upright, distorted,diminished and virtual.What is an electric current?A electric current refers to the rate of flow of electric charges through a conductormotivated by a voltage and is measured in amperesAn electric current generates a magnetic fieldBut to MAKE USE of the magnetic field, you need to coil it
To make even better use by guiding the magnetic field lines, use a iron nail at the core of thecoils. This helps to form an electromagnet. Without the iron nail, there is very close fieldlines. The closer the lines, the stronger the magnetic attraction.