physics paper 2

• Waves transfer ____ energy from place to place, without transferring any matter
• What is the amplitude? The amplitude of a wave is the distance from the centre line (or the still position) to the top of a crest. or to the bottom of a trough.
• What is frequency? Frequency is the number of complete waves passing a certain point per second measured in Hz. 1 Hz is equal to 1 wave per second.
• What is wavelength? The wavelength of a wave is the distance between a point on one wave and the same point on the next wave.
• Wave speed formula
• What are transverse waves? Transverse waves are waves whose oscillations are at right angles to the direction of travel and energy transfer.
• What are longitudinal waves? In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer. (parallel)
• Examples of transverse waves All EM waves and ripples on water
• Examples of longitudinal waves Sound waves, seismic waves, P- waves
• What is the frequency range of human hearing? 20Hz - 20KHz
• What is reflection? Reflection involves a change in direction of waves when they bounce off a barrier.
• What is refraction? Refraction is the process by which a wave changes speed and sometimes direction upon entering a denser or less dense medium.
• Reflection experiment
• What is the angle of incidence? The angle of incidence is the angle between the incoming wave and the normal.
• What is the angle of reflection? The angle of reflection is the angle between the reflected wave and the normal.
• Angle of Incidence is greater/equal/less than the Angle of Reflection Angle of Incidence = Angle of Reflection
• What is the law of reflection? The law of reflection states that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray.
• What is specular reflection? Specular reflection happens when a wave is reflected in a single direction by a smooth surface E.g when light is reflected by a mirror you get a nice clear reflection
• Specular and diffuse reflection image
• What is diffuse reflection? Reflection from a rough surface is called diffuse reflection because the reflected rays are scattered in lots of different directions
• Electromagnetic Spectrum
• 3 things all electromagnetic waves have in common
• What is the speed of light in a vacuum or air? 300,000,000 m/s
• Which colour is the best absorber of radiation? Black
• What gases in the atmosphere change the balance of infrared radiation absorbed and emitted by the Earth? Greenhouse gases change the balance of infrared radiation absorbed and emitted by the Earth.
• Uses of radio waves Radio waves are used for communication such as broadcasting television and radio, communications and satellite transmissions.
• What health effects can ultraviolet waves cause? Cause the skin to age prematurely and increase risk of developing skin cancer
• What is echo? A reflection of sound waves from a smooth surface
• Uses of infrared - security systems - thermal imaging - electrical heaters
• Define ultrasound Ultrasound is sound with a frequency greater than 20,000 Hz
• What type of radiation is used to transmit a signal in an optical fibre? Visible light
• What is the critical angle? The minimum angle at which total internal reflection takes place
• Uses of total internal reflection
• What are the two types of seismic waves? P-waves and S-waves
• Similarities and differences between P and S waves
• What is a black body? An object that absorbs all radiation falling on it, at all wavelengths, is called a black body.
• What happens when an object is at a constant temperature? This means that the object is absorbing radiation at the same rate at which it is emitting radiation.
• What is a lens? A lens is a transparent block that causes light to refract to form an image.
• Why are microwaves used for satellite communication and not radio waves? Microwaves pass straight through the atmosphere and are suitable for communicating with distant geostationary satellites, while radio waves are suitable for communicating with satellites in low orbit.
• What properties make radio waves ideal for communication? Radio waves are transmitted easily through air. They do not cause damage if absorbed by the human body, and they can be reflected to change their direction.