The lenses of eyeglasses and other optical instruments are based on the refraction of light. Real images are those that can be cast on a screen. Virtual images cannot be reproduced on a screen. The phenomena of diffraction can be used to measure the wavelength of a color of light. Diffraction is defined as the spreading of a wave into a region behind an obstacle.
Interference is the superposing of one wave on another.
Interference can be constructive or destructive. Magnetism Like magnetic poles repel and unlike magnetic poles attract. Magnetic fields run out from the north pole and enter a magnet's south pole. Closed loops are formed by magnetic field lines. This chapter will review these basic properties of magnets.