In doing so, a longitudinal wave is produced.Ģ. ruler or tuning fork) vibrates, a series of compressions (high air pressure) and rarefactions (low air pressure) are produced by shifting of air layers. Sound is produced by vibrating sources placed in a medium. Describe how a vibrating object produces sound waves. Travel at an approximate speed of 3 x 10^8 m/s through airĭoes not need any medium to travel. Needs a medium to travel, cannot travel through vacuum Travel at an approximate speed of 330m/s through air State 3 ways in which an electromagnetic wave differs from the sound wave. Red light has a longer wavelength (or lower frequency) than blue light.Ĥ. State one difference between waves of red light and waves of blue light. When an EM wave enters glass, its speed is slowed down while its frequency remains constant.ģ. How do the frequency, wavelength and speed of electromagnetic waves change when it enters from air to glass? State the properties which are common to all forms of electromagnetic radiation.Īll travel with the same speed, 3 x 10^8 m/s in vacuum.Ģ. (many physics questions will state to avoid this economical reason)ġ. Optical fibres are cheaper to manufacturer. Optical fibres are lighter and hence easier to install. Optical fibres experience less signal loss Optical fibres can carry much more information than copper wires. State the advantages of using optical fibres over copper wires in telecommunications. Periscope – prisms are positioned to reflect light and give clear images. Telecommunication – transmission of signal.Įndoscope – to see organs in the body by directly light through a thin plastic tube into the body.īinoculars – prisms allow for TIR and reduce length of the instrument. The diamond is also cut in such a way that when light enters, it will undergo TIR a few times before most of them emerge from the top surface. Having high refractive indexes, diamonds have small critical angles.Ī large proportion of light at the diamond-air boundary will have incident angle greater than that of the critical angle, hence undergoing TIR. *Why do diamonds have such brilliant sparkle? When the incident angle is more than the critical angle, TIR will then take place. This incident angle is called the critical angle. This is essential for the refracted angle in the less dense medium to be 90 degrees for a given incident angle in the denser medium. Only when light travels from denser to less dense medium, then will it bend away from the normal. Its speed in air is 3.0 x 10^8 m/s while its speed in glass is lower at 2.0 x 10^8 m/s.Īt the boundary of the two media, the sudden change in speed causes the path of light to bend.Įxplain why TIR can only take place when light is traveling from denser to less dense medium Light travel at different speeds in different optical media. This distance can even be longer than the room itself.Įxplain why refraction takes place when light travel from air to glass. The larger distance between the viewer and the test card can be obtained. In this way, it can appear further than it actually is. When a plane mirror is used, the image of the optical test card will be at a distance equal to the object distance. State one advantage of using a plane mirror in optical testing. State the properties of the image formed by a plane mirror
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