Term
4.1.2 Define the terms displacement, amplitude, frequency, period and phase difference. 

Definition
displacement: the instantaneous distance of a moving object from its mean position in a specified direction. frequency: the number of oscillations completed per unit time period: the time taken for one oscillation phase difference: a measure of how in step different particles are 


Term
4.1.3 Define simple harmonic motion (SHM) and state the defining equation as a = −w^2x . 

Definition
The motion that takes place when acceleration a is always directed towards and proportional to its displacement from a fixed point. 


Term
4.3.1 State what is meant by damping. 

Definition
It is sufficient for students to know that damping involves a force that is always in the opposite direction to the direction of motion of the oscillating particle and that the force is a dissipative force. 


Term
4.3.3 State what is meant by natural frequency of vibration and forced oscillations. 

Definition
a system oscillates at its natural frequency of vibration when it is temporarily displaced from its equilibrium position and released. Forced oscillations occur when the system is subject to an external force that varies with the chosen frequency. 


Term
4.3.5 State what is meant by resonance. 

Definition
When a system is forced to oscillate at its natural frequency. 


Term
4.4.2 State that progressive (travelling) waves transfer energy. 

Definition
Students should understand that there is no net motion of the medium through which the wave travels. 


Term
4.4.6 Define the terms displacement, amplitude, frequency, period, wavelength, wave speed and intensity. 

Definition
disp: the change that has taken place as a result of a wave passing a particular point. amplitude: the maximum displacement from the mean position frequency: the amount of oscillations per unit time period: the time taken for one complete oscillation wavelength: the shortest distance along the wave between two points that are in phase. wave speed: the speed at which wavefronts pass a stationary observer intensity: power per unit area that is received by the observer INTENSITY IS PROPORTIONAL TO AMPLITUDE^2 


Term
4.4.9 State that all electromagnetic waves travel with the same speed in free space, and recall the orders of magnitude of the wavelengths of the principal radiations in the electromagnetic spectrum. 

Definition
visible light: 107 – 106 

