Waves Flashcards
What are the 2 types of waves?
Transverse & longitudinal
Sinusoidal Waves?
Periodic displacement at Period P or Frequency F
P= 1/f
Distance between troughs = λ
What is a wave?
A disturbance which transfers energy from one place to another without any net motion of the medium through which it travels
Velocity of waves
V (m/s)= f(/s)λ(m)
Sound intensity?
dB = 10 log (I/I0)
I0 = threshold of human hearing
How to calculate wave intensity?
I (W/m) = L(W)/4πr^2
Intensity of a eave = energy it carries m^-2 s^-1 / W m^-2
What does isotropic mean?
Wave energy emitting equally in all directions
What is a transverse wave?
motion in which all points on a wave oscillate along paths at right angles to the direction of the wave’s advance - water/ light
What is a longitudinal wave?
waves where the particle motion is in the same direction in which the wave is propagating e.g. sound - vibration
What is constructive interference?
Waves are in phase and add constructively - same f,λ but different amplitude
What is destructive interference?
When waves are exactly out of phase - now amplitudes cancel & waves add destructively?
What does a ray of light have perpendicular to it?
An electric field and a magnetic field - electromagnetic radiation
What are the Laws of Reflection?
- θi = θr
- incident & reflected ray & normal all lie in the same plane
What are the law’s of refraction?
- Snell’s Law n1sin (θ1) = n2sin(θ2)
- incident & reflected ray & normal all lie in the same plane
How to calculate the refractive index?
n = speed of light in vaccuum/ speed of light in medium
What is the critical angle?
The angle of incidence which will cause the angle of refraction to be 90° from the normal
=sin^-1(n2/n1)
What happens if the incident angle is greater than the critical angle?
Total internal reflection occurs
What is a prism?
A transparent object with 2 plane surfaces inclined at an angle
the angle between the undeviated and the ray deviated is directly proportional to size of the angle between the planes
What is a convex lens?
() converging lens - all pass through a point on the axis of symmetry called a focal point
What is a concave lens?
)( diverging lens
What is a lens?
Glass bounded by 2 spherical surface
What is focal length?
The distance between the centre of the lens and the focal point - rays parallel - 2 foci
What ray is undeviated in a lens?
The one that passes through the centre
Do diverging/concave lenses have foci?
Rays diverge at lens but appear to originate at F
Rule for image formation?
3 lines
1. ray parallel to optical axis then refracted through F
2. Passes through the centre of the lens undeviated
3. Passes through F initially - emrges parallel to optical axis
How to calculate magnification?
M= hi/ho = distance between lens & image/distance between lens & object
Thin lens equation?
1/u + 1/v =1/f
What is a real image?
When rays actually converge - convex () lens - f>0 using thin lens
What is a virtual image?
Image appears to be formed at a location but not physically there - f<0 using thin lens - v<0 for virtual image
If ratio between lambda is 1,2,3,4,… Between 2 waves?
They are constructive
If the ratio of lambda between 2 waves is 0.5,1.5,2.5,…. ?
Destructive interference
Measure the distance between crests?
Distance between Maxima= distance between crests x distance to screen / distance between slits
