Ray Box Investigations For Reflection - Refraction and Total Internal Reflection

Ray Box InvestigationsForReflection - RefractionandTotal Internal Reflection Created for CVCA Physics By Dick Heckathorn 1 June 2K + 5

#1 #2 30o 30o 60o 60o #3 Rays 1-2-3

Conclusion The angles are measured from the normal. The angle of incidence equals the angle of reflection.

Reflection r N i

Conclusion The angles are measured from the normal. The angle of incidence equals the angle of refraction. The incident ray, reflected ray and the normal all lie in the same plane.

Extend reflected rays behind mirror Locate reflection surface of mirror on line. Reflect ray of light from mirror as shown. Insert a pin (1) on reflected light ray. Draw a line from object to image Mark and draw the light rays on paper Insert pin into cardboard as shown. Remove mirror The image is located where the rays cross. Draw a line across center of paper Repeat for rays 3 and 4. Insert pin (2) on ray and draw it. Reflect a 2nd ray from mirror as shown Repeat for other three occurrences How is this line oriented relative to mirror line? How does length of red and purple line compare? Draw normal lines and compare angle ‘i’ and ‘r’ Image Mirror i r Pin 2 4 3 1

Conclusion The image is always as far behind the reflecting surface (mirror) as the object is in front. The line connecting the image and object is perpendicular to the reflecting surface (mirror).

Locate object. Repeat for eye 2, 3, and 4 Draw line representing mirror. Connect eye (1) and image Draw line from object to mirror Light travels this path from object to pin Note angle ‘i’ equals angle ‘r’ Then draw line from mirror to eye 1 Locate image Locate eye (1) Why know where the image is? Image Mirror surface r i Object Pin 3 1 4 2

Conclusion Locating the image allows one to predict the path light will travel from the object to some location.

I1,2 I1 Mirror (1) I2 Object Mirror (2)

Mirror (1) Mirror (2) I1,2 I2 I1 Object

Periscope I1 Object I1,2

Pepper Ghost Bottle of Water 90o Plexiglas Candle

Peppers Ghost

T29-1B

#19 V P.A. F f All rays parallel to P.A. reflect back through ‘F’

Parabolic Mirror #20

Circular Mirror P.A. Not all rays parallel to P.A. reflect back through ‘F’

Circular Mirror P.A.

Go to curved mirror PowerPoint. Click

N #4 i r Measure angle i and angle r. Both = 0o

#5 N 300 i r 19.50 Calculate Measure angle i and angle r.

N #6 600 i r 35.30 Calculate Measure angle i and angle r.

for both angles, Using what value did you get? It should be near 1.50 1.50 is called the index of refraction (nP) of the plastic.

N Quiz 750 40.10 Calculate the angle of refraction. Draw an incident ray of 75o. Test your drawing with a light ray. Draw the refracted ray.

N Calculate angle of refraction Use light ray to check. Bent away/toward normal? Draw the refracted ray 30.90 30.90 200 #8

n1 sin θ1 = n2 sin θ2 It tells us which way the refracted ray bends. Does it all!!! What does it do? How? The bigger ‘n’ has the smaller ‘sin θ’ and thus the smaller ‘θ’ (angle).

N Bent away/toward normal? Calculate angle of refraction Draw the refracted ray Use light ray to check. 74.60 74.60 400 #9

N Bent away/toward normal? Use light ray to check. Now what do we do? Calculate angle of refraction Tilt!! 600 600 #10

N What happens here? 750 750 #11

Demonstrations • T.I.R. Plastic • T.I.R. Water • T.I.R. Glass Tube • Ball in/out of Water • Mugs

Demo – Aquarium Balls Aquarium Balls Air Water

300 #12 Draw the refracted ray. Calculate angle of refraction Which way is ray bent? n=1.50 19.50 Check with ray box. Calculate angle of refraction Which way is ray bent? Draw the refracted ray. 300

#13 600 600 00 Calculate angle of refraction Calculate angle of refraction n=1.50

11.80 18.20 280 17.80 #15 11.80 18.20 280 17.80 #14 n=1.50 Calculate angle of refraction Calculate angle of refraction Calculate angle of refraction Calculate angle of refraction

#18

That’s All Folks!! No 16-17

Ray Box Investigations For Reflection - Refraction and Total Internal Reflection