Physics (9.3.23) Flashcards
What are waves?
Waves tranfer energy and information without transferring matter (particles oscillate about a fixed point)
What is a Transverse wave?
-Have peaks and troughs
-Oscillations (vibrations) are perpendicular to the direction of energy (wave)
-Eg: light
What are Longitudinal waves?
-Consists of compressions and rarefractions
-Oscillations (vibrations) are parallel to the direction of energy (wave)
-Eg: sound
What is the Amplitude of a wave?
the distance from the equilibrium position to the maximum displacement
What is the Wavefront of a wave?
the front of a wave, or the same point on each wave
What is the Frequency and its units?
-The number of waves passing through a point per second
-Hz (hertz)
What is the Wavelength?
The distance between two adjacent peaks on a wave
What is meant by the period of the wave?
The length of time it takes for one full wave to pass through a point
How can you calculate the wave speed?
speed = frequency x wavelength
v = f x λ
State an equation linking frequency and period of a wave
Frequency (Hz) = 1/ period (s)
f = 1/T
What are Mechanical waves?
-waves that need to pass through a material
-made from vibrations of that material
-eg: sounds waves, seismic waves, strings
What are Electromagentic waves?
-Transverse
-Travel at the speed of light in vacuum
-Can be reflected, refracted or diffracted
speed = 3x10 (to the power of 8) m/s
What is the order of the Electromagnetic spectrum?
Radio wave, Microwave, Infrared radiation, Visible light, Ultraviolet, X-Ray, Gamma Ray
Uses of Radio waves and Microwaves
-broadcasting and communications
-cooking and satellite transmissions
Uses of Infrared, Visible light, and Ultraviolet
-heaters and night vision equipment
-optical fibres and photography
-fluorescent lamps
Uses of X-Rays and Gamma rays
-observing the internal structures of object and materials, including for medical applications
-sterilising food and medical equipment
Detrimental effects of microwaves and simple protections
internal heating of body tissue - using an oven
Detrimental effects of Infrared and Ultraviolet and simple protections
-skin burns - protective clothing
-damage to surface cells and blindness - sunscreen
Detrimental effects of Gamma Rays and simple protections
cancer, mutation - led, concrete
What does the Law of Reflection state?
Angle of incidence = angle of reflection
State an equation linking angle of incidence, angle of refraction and refractive index (law of refraction)
refractive index = sin (angle of incidence)/ sin (angle of refraction)
n = sin(i)/sin(r)
What is the total internal reflection?
-happens when light goes into a substance with a lower refractive index (eg: glass into water into air)
-happens when the angle of in. is larger than the critical angle
-light will keep reflecting
What is the Critical angle?
The angle of incidence which causes the angle of reflection to be 90º so that the light refracts onto the boundary
< c.a = reflection > c.a = refraction
State an equation linking critical angle and refractive index (critical angle)
refractive index = 1/ sin(critical angle)
n = 1/ sin(c)
What is the Refraction of sound?
-sound can also refract (change direction) when it travels to a different media
-sometimes, it can refract due to a change in temperature
What is meant by “the doppler effect”
wave source is moving towards observer -> observed frequency increases and observed wavelength decreases and vv since v = f×λ and speed is constant
-if speaker and mic are getting closer = higher pitch
-if speaker and mic are getting further = low pitch
State the equation for the period
T = 1/f
Why would you sterilise food?
It kills microbes in it and it will stay fresh longer
How do glass blocks affect the rays?
They usually:
-waves travel at different speeds in materials with diff. densities
-when a wave crosses a boundary into another medium the speed and direction change
-this is refraction
