P5.3 Wave Interaction Flashcards
Why are EM waves refracted?
When light goes from a less dense medium to a more dense medium, it slows down and bends towards the normal. If the density change is larger, so is the change in direction.
What affects whether an EM wave is absorbed, reflected or refracted?
The direction and its wavelength
What is the difference between a concave and convex lens?
A convex lens refracts by converging rays to a focal point.
A concave lens refracts by diverging rays to producing a virtual focus behind the lens
What is the focal point?
The focal point is the point where light refracted by a convex lens converges
What is the optical centre?
The optical centre is the central point of the lens
What is the principal axis?
The principle axis is the perpendicular line of light passing through the optical centre
What is the virtual focus?
The virtual focus is the point where divergent light centres from behind the concave lens
What is the focal length?
The focal length is the distance between the optical centre and focal point or virtual focus
How do lenses correct vision?
Myopia cannot focus on distant objects. People are given a concave lens.
Hyperopia cannot focus on nearby objects. People are given a convex lens.
What are the steps to drawing a ray diagram?
Draw a ray from the top of the object parallel to the principle axis to the lens. Then from the lens to the focal point
Draw a ray from the top of the object through the optical centre and straight through
Where the two rays cross or appear to come from is the top of the image
The bottom of the object is on the principal axis
What are the orders of colours from lowest frequency to highest frequency?
Red
Orange
Yellow
Green
Blue
Indigo
Violet
What is the difference in speed and refraction of different colours?
Colours with a higher frequency are refracted more. Therefore, they move faster in glass
What is dispersion and spectral colours?
When white light is refracted by glass, it spreads out into a spectrum by the process of dispersion. The colours associated with the white light spectrum are known as the spectral colours
What are the types of reflection?
Reflection from surfaces depends on the type of surface. You can see images in mirror because the reflection is specular. You cannot in other objects because the scattering is diffuse
