Light waves (chapter 12) Flashcards
What are luminous objects?
Objects which emit their own light.
How do we see non-luminous objects?
We see non-luminous objects because of the light they reflect.
What happened when a ray of light strike a mirror?
angle of incidence = angle of reflection
What is refraction?
When a ray of light travel across the border between two different medium, the change in speed cause the ray to change direction.
What is the speed of light in glass?
200 million m/s
What happens if the ray strikes the boundary between the two media at 90 degrees?
The ray continues without a change of direction.
How is the amount of refraction described?
Refraction index
Refraction occurs at —– medium.
2
State the formula to find refractive index?
n = sin i / sin r
Which object is needed for reflection of rays?
Mirror
What are transparent objects?
- Water
- Ice
- Glass
- Diamond
Which surface does regular reflection and diffused reflection occur?
Regular reflection - smooth surface
Diffused reflection - rough surface
Which kind of waves doesn’t need medium?
EM waves
What is refractive index?
Amount that use to describe how much do different materials can bend rays of light.
What is total internal reflection?
Total internal reflection occurs when rays of light are travelling towards a boundary with a less optically dense medium.
What is critical angle?
The critical angle is the smallest possible angle of incidence at which light rays are totally internally reflected.
What happen when Angle of incidence (i) is greater than the critical angle?
All the light is internally reflected at the boundary and no light is refracted.
What are conditions needed for total internal reflection?
- (i) > (c)
- Light must travel from more dense to less dense medium
What are the equipment to investigate total internal reflection?
- Semi-circular glass box
- A ray box
What is the formula to find critical angle?
sin c = 1/ n (refractive index)
How much is the critical angle for light passing from glass to air.
42 degree
Why is it better to use prisms in a periscope?
The images produced by prisms are often brighter and clearer than those produced by mirrors.
What are the uses of total internal reflection?
- Prismatic periscope
- Bicycle and car reflectors
- Binoculars
- Optical fibers
- Endoscope
- Telecommunications
How is optical fiber composed of?
It is composed of 2 different type of glass which the center has high refraction index glass surrounded by glass with low refraction index.
What does each side of a pair of binoculars contain?
Two prisms to totally internally reflect the incoming light.
How will the binocular without the prisms be like?
Without the prisms, the binoculars would have to be very long to obtain large magnifications.
How is it make sure that light entering the inner core in optical fiber is always internally reflected?
As the fibers are narrow, light entering the inner core always strike the boundary of the two glasses at an angle that is greater than critical angle.
What is the benefit of the use of endoscope?
- less stressful for patients
- usually leads to a more rapid recovery.
Why modern telecommunications systems use optical fibers rather than copper wires?
Less energy is lost by using optical fibers.
How are electrical signals from telephone are converted?
They are converted into light energy produced by tiny lasers.
What changes the pulses of light back in electrical signals in optical fiber?
Light-sensitive detector at the other end.
How much is the critical angle for light passing from water to air?
49 degree
What is the relationship between refractive index (n) and critical angle (c).
Inversely proportional
What is the relationship between density and refractive index (n).
Directly proportional
