# Waves

This Mindmap sums up almost everything you need to know for Section 3- GCSE Physics

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• Waves
• Properties of waves
• Describing Transverse and Longitudinal Waves
• Transverse waves vibrate at right angles to the direction at which the waves is moving
• Longitudinal Waves vibrates in the direction in which the wave is travelling
• Key Words
• Amplitude--the maximum extent of a vibration or oscillation, measured from the position of equilibrium.
• Frequency-- The number of waves produced each second by a source or the number passing a particular point each second.
• Wavelength: The distance between a particular point on the wave and the same point on the next wave.
• Period of a wave-the time needed for one complete cycle of vibration to pass a given point.
• Formulas need to know
• wave speed= frequency + wavelength
• Frequency= 1 / time period
• The Electromagnetic Spectrum
• Light is a continues part of the spectrum which includes Radio waves, microwaves, Infrared red, Visible light, Ultraviolet, X-rays and Gamma rays
• Order as per decreasing wave length and increase in frequency:- Gamma Rays, X-rays, Ultraviolet, visible light, Infrared red, microwaves and radio waves
• Uses
• Microwaves-Cooking and satellite transmissions
• Infrared Light- Heaters and night vision equiment
• Visible Light- Optical fibers and photgraphy
• Ultraviolet: Fluorescent Lamps
• X-rays- Observing the internal structure of an object
• Gamma rays- Sterilising fool and medical equipment
• Effects of Expose to:..
• Microwaves-Internal heating of body tissue
• Infrared: Skin burns
• Ultraviolet: Damage to surface cells and blindness
• Gamma Rays: Cancer and Mutation
• Light
• Light waves are transverse waves which can be reflected, refracted and diffracted
• The Law of Reflection
• When a ray of light strikes a plane (flat) mirror, it is reflected so that the angle of incidence is equal to angle of refraction.
• Formula Need to know:
• n= Sin (i) / Sin r
• Total Internal Refection
• Optical Fibers
• Used in communicating
• Electrical signals from a telephone are converted into light energy by tiny lasers, which send pulsars of light into the end of the optic fiber
• Prisms
• Separates white light into its 7 colors because the prism has slightly different refractive index for each of the colors.
• Critical Angle
• The value of the critical angle depends upon the media of assuming that the less dense medium into air then it is 42 as an angle or for water it is 49 degrees
• Sound
• Difference between analogue and digital sound
• Analogue Sound- the information is converted into electrical voltages  or currents that vary continuously.
• Digital Sound- The information is converted into a sequence of numbers called a binary code. This code uses just 0 or 1 rather than the ten digits we normally use.
• Advantages of using digital signals-  The signal during transmission become weaker and have to be regenerated which digital sounds creates a clean signal again.
• Sound travels though solids, liquids and gases. It needs molecules/ atoms to pass on vibrations
• Sound cannot travel though a vacuum
• Light is much much faster than sound
• Speed of sound in air- 330-340 m/s
• Human hearing ranging from 20Hz- 20,000 Hz.
• Experiment about measuring speed of sound in air:- Measure a distance of the area from where the person with the air horn will stand with the students at the other end measuring how long it takes the sound to travel to them.
• Relating to loudness
• The louder, the sound is the higher amplitude and the quite sounds, the softer sound will be captured
• Period of a wave-the time needed for one complete cycle of vibration to pass a given point.
• Light is a continues part of the spectrum which includes Radio waves, microwaves, Infrared red, Visible light, Ultraviolet, X-rays and Gamma rays