Reflection, refraction, converging lenses Flashcards
What is the incident ray
Light ray going towards the surface
What is the reflected ray
Light ray going away from surface
What is the point of incidence
Point at which incident ray strikes the surface
What is the normal
Perpendicular line at surface at point of incidence
What is the angle of incidence
Angle between incident ray and normal
What is the angle of reflection
Angle between reflected ray and normal
What are the laws of reflection
- Angle of incidence = angle of reflection
- Incident ray, reflected ray and normal at point of incidence all lie in the same plane
What are the characteristics of an image formed in a plane mirror
- Same size
- Upright
- Virtual
- Laterally inverted
- Image distance = object distance
Define refraction
Refraction is the bending of light as it travels from one medium to another medium of different optical density
What happens when light travels from an optically less dense medium to an optically denser medium
- Speed of light decreases
- Light bends towards normal
What happens when light travels from an optically denser medium to an optically less dense medium
- Speed of light increases
- Light bends away from normal
Define refractive index
Refractive index is the ratio of the speed of light in vacuum to the speed of light in the medium
What is the speed of light in vacuum
3.0x10^8 ms^-1
Define focal length
Focal length is the distance between the optical centre C and the principal focal point F
What are the laws of refraction
- Incident ray, reflected ray and normal at point of incidence all lie in the same plane
- For 2 given media, ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant
Define total internal reflection
Total internal reflection is the complete reflection of a light ray in an optically denser medium at the boundary with an optically less dense medium
How does refractive index affect critical angle
Smaller refractive index
= Larger critical angle
Define critical angle
Critical angle is the angle of incidence in an optically denser medium for which the angle of refraction in the optically less dense medium is 90 degrees
What are the conditions for total internal reflection
- Light travels from optically denser to an optically less dense medium
- Angle of incidence in optically denser medium is larger than critical angle
Why are glass prisms better light reflectors than mirrors
- Produce only 1 reflection
- Do not have a silver surface that wears off
What are optical fibres
- Long and thin device that relies on total internal reflection to transmit signals
Advantages of using optical fibres over copper wires in telecommunication
- Data transfer rate is 10 to thousands of times faster using optical fibres
- Less signal loss than copper wires
- Lighter and cheaper
- Carry more information over long distances
- Immune to electromagnetic interference
Advantages of using optical fibres in medicine
- Thin and light, so it is minimally invasive
- Flexible to curve around obstacles
Define a lens
A lens is a piece of clear plastic or glass which curved surfaces for converging or diverging light rays
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