Pasco OS-8536 OPTICS TABLE Manuel d'utilisateur télécharger pdf (Page 15)

012-06557A Optics Table

Rotate the Ray Table until the light ray emerging from the Cylindrical

Lens just barely disappears. Hold a piece of white paper next to the edge

of the Ray Table so you can see the light ray.

Just as it disappears, the ray separates into colors. The table is rotated far

enough if the red color has just disappeared.

Use the pencil to trace the edges of the Cylindrical Lens onto the Ray

Table. Mark the point on the table where the light ray is internally re-

flected. Also mark the entrance point of the incident ray and the exit point

of the reflected ray.

Remove the Cylindrical Lens and draw the rays that are incident upon and reflect off the inside flat surface of

the Cylindrical Lens. Measure the total angle between these rays using a protractor. Note that this total angle is

twice the critical angle because the angle of incidence equals the angle of reflection.

Experiment 7: Refraction – Convex and Concave Lenses

EQUIPMENT NEEDED

– Light Source – Optics Bench

– Ray Table and Base – Convex Lens

– Concave Lens – ruler

Purpose

To explore the difference between convex and concave lenses and to determine their focal lengths.

Theory

Parallel rays of light passing through a thin convex lens cross at the focal point of the lens. The focal length is

measured from the center of the lens to the focal point.

Procedure

Mount the Light Source, Ray Table Base, and Ray Table on the Optics Bench. Place the Convex Lens on the

edge of the Ray Table nearest to the Light Source. Shine five light rays from the Light Source straight into the

convex lens. Trace the outline of the lens and trace the incident and transmitted rays. Indicate the incoming and

the outgoing rays with arrows in the appropriate directions.

The place where the five refracted rays cross each other is the

focal point of the lens. Measure the focal length from the cen-

ter of the convex lens to the focal point.

Repeat the procedure for the concave lens. Put the concave

lens about two-thirds of the way across the Ray Table from the

Light Source. Note that the rays leaving the lens are diverging

and they will not cross. After you trace the outline of the lens

and the incident and refracted rays, use a ruler to extend the

outgoing rays straight back through the outline of the lens. The

focal point is where these extended rays cross.

Nest the convex and concave lenses together and place them in

the path of the parallel rays. Trace the rays. What does this tell

Double

Convex

Lens

OS-8517

PATTERN

LIGHT

SOURCE

COLOR

TO REPLACE BULB SEE

INSTRUCTION MANUAL.

BULB: 12V 10W G-4

DO NOT TOUCH BULB

WITH FINGERS.

DISCONNECT POWER

BEFORE CHANGING BULB.

5 3 1

RAY

SLITS

Five parallel rays

Figure 7

Ray

Box

Exit point

Reflected Ray

Total Internal

Reflection

Entrance point

Figure 6.3

2θ

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 21 22

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Pasco OS-8536 OPTICS TABLE Manuel d'utilisateur Page 15

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