# Physics: Waves & the Universe

HideShow resource information
• Created by: Lily
• Created on: 12-03-13 16:14
• Physics: Waves & the Universe
• WAVES
• WHAT ARE THEY? Oscillations that move + transfer energy.
• LONGITUDINAL WAVES
• EXAMPLES: Sound waves, P(primary) waves, Ultrasound waves.
• WHAT? The oscillations are parallel to the direction of the wave. Involves compressions+ rarefactions.
• TRANSVERSE WAVES
• EXAMPLES: Electromagnetic waves, S(secondary) waves & Water waves
• WHAT? Oscillations are at right angles to the direction of the wave
• ELECTROMAGNETIC WAVES (Radio, Microwave, Infra-red, Visible light, Ultraviolet, X-ray, Gamma Rays)
• All travel at the speed of light - 3x10 to the power of 8
• RWaves, MWaves, I-RED and VLight used for communication.
• WHAT CAN WAVES DO?
• DIFFRACTION
• Significant diffraction only occurs when the wavelength of the wave is same order of magnitude as the size of the gap or obstacle.
• REFLECTION
• Angle of incidence = angle of reflection
• Image produced in plane mirror = virtual, upright + laterally inverted.
• REFRACTION
• Waves not refracted if travelling along normal.
• eaves change direction when refracted in another medium
• WAVE SPEED = FREQUENCY X WAVELENGTH
• SOUND WAVES
• Causes VIBRATIONS in a medium = sound.
• Frequency of SW = pitch,   Amplitude of SW = loudness.
• Echoes = reflections of SW
• THE UNIVERSE
• Doppler effect = source moving away from observer , so there is change in wavelength + frequency.
• Source moving AWAY = INCREASED wavelength + DECREASED frequency. OPPOSITE for moving TOWARDS.
• DE causes red-shift in galaxies, where light's wavelength increases.
• Galaxy further away = moving faster away. Gives evidence of expanding Universe.
• THE BIG BANG
• All matter focused at one super dense, super hot tiny fixed point. Point exploded, expanded + cooled to form Universe. Theory supported by red shift and CMBR.
• Galaxy further away = moving faster away. Gives evidence of expanding Universe.
• Cosmic Microwave Background Radiation (CMBR) = Form of EM radiation filling Universe. Comes from radiation present shortly after beginning of Universe.