Angle of refraction and incidence-help

Question

1. The diagram shows a beam from a flashlight striking a piece of glass(n=1.5} at an angle of 40°.

Diagram: http://www.flickr.com/photos/99973477@N03/10302501525/

a) how big is the angle of incidence?

b) how big is the angle of refraction?

2. Light travelling through air strikes a piece of plastic at an angle of 45°. As it passes into the plastic, its angle of refraction is 36°. 

a) what is the refractive index of the plastic?

3. What is the the critical angle for:

a) water(n=1.33) to air:

b) glass(n=1.50) to air:

c) diamond(n=2.42) to air:

4. A stationary fish in a clear pond decided to look upward towards the water surface. Shown in the diagram are four rays of light that reached the fish which went through the points A,B,C and D.

Diagram: http://www.flickr.com/photos/99973477@N03/10302516126/

The ray passing through C has an angle of refraction slighlty less than the critical angle so the air is almost parallel to the surface. The diagram has not not drawn the path of the light before it reached A,B or D.

a) On the diagram, draw in the three ras that pass through A, B and D before they go to the fish.

b) the fish's view of the scene above is distorted. Explain why this is so.

5. Consider the following diagram. All boundaries between the media are parallel, normal lines have been drawn.

The angle of incidence from air to water: iaw=42°

Diagram: http://www.flickr.com/photos/99973477@N03/10302517206/

a) Calculate the angle of refraction in the water.

b) what is the angle of incidence from water to glass?

c) calculate the angle of refraction in the glass.

d) what is the angle of incidence from glass to air?

e) calculate the angle of refraction of the ray as it emerges in the air.

Answer 1

2)

a) Calculate the refractive index of the plastic by using snell's law,

n=sin i /sin r

Substitute 45 for i and 36 for r.

n= sin 45/sin 36 =1.2

Therefore, refractive index is 1.2

 

Answer 2

3)

Critical angle ,θ=sin^-1(nr/ni)

For air,nr=1

a)

Substitute 1 for nr and 2.42 for ni

θ=sin^-1(1/2.42)=48.75

b)

Substitute 1 for nr and 1.5 for ni

θ=sin^-1(1/1.5)=41.81

c)

Substitute 1 for nr and 2.42 for ni

θ=sin^-1(1/2.42)=24.41

Answer 3

5)

a)

Calculate the angle of refraction in the water,

Using snell's law,

(nair/nwater)=sinθr/sinθi

1/1.33=sin θr/sin42

sin θr=sin42/1.33=0.5

θr=30

b)

Calculate the angle of incidence from water to glass,

Angle of  incidence from water to glass=Angle of refraction in the water

Angle of  incidence from water to glass= 30

C)

calculate the angle of refraction in the glass,

Using snell's law,

(nwater/nglass)=sinθr/sinθi

1.33/1.52=sin θr/sin30

sin θr=sin30*1.33/1.52=0.4375

θr=25.9

d)

Calculate the angle of incidence from glass to air,

Angle of  incidence from glass to air=Angle of refraction in the glass

Angle of  incidence from glass to air= 25.9

Answer 4

5)

e)

calculate the angle of refraction of the ray as it emerges in the air.

Using snell's law,

(nglass/nair)=sinθr/sinθi

1.52/1.00=sin θr/sin25.9

sin θr=sin25.9*1.52/1=0.662

θr=41.68

Answer 5

1).

a).

Angle of incidence : Angle of of incidence is the angle at which a beam of light hits a surface.

Observe the above diagram, The angle of incidence  = 90 - 40 = 50⁰ .

b).

Angle of refraction : Angle of refraction is the angle a beam of light bends when it goes through a different medium (such as going from air to water).

From the figure, angle of refraction is θ.