Analysis, Part 2: ray-tracing method procedure – PASCO OS-8515C Basic Optics System User Manual

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B a s i c O p t i c s S y s t e m

E x p e r i m e n t 9 : A p p a r e n t D e p t h

Figure 9.2

With both eyes, look down through the top of the trapezoid. Does the line viewed
through the trapezoid appear to be closer? Close or cover one eye, and move your
head side to side. Do you see parallax between the line viewed through the trape-
zoid and the line viewed directly?

In this step, you will hold a pencil near the trapezoid to determine the position of
the apparent line. When the pencil and the apparent line are at the same distance
from your eye, there will be no parallax between them.

While looking down through the trapezoid (with one eye), hold a very sharp
pencil as shown in Figure 9.3 so it appears to be lined up with the line inside the
trapezoid. Move your head left and right to check for parallax. Move the pencil
up or down and check again. When there is no parallax, mark that point. (Hold
the trapezoid with your free hand, press the pencil tip gently against the side of
the trapezoid and twist the pencil to make a light mark. Erase the mark after you
have finished this experiment.)

Analysis

Measure the distance from the top of the trapezoid to your pencil mark. Record
this apparent depth, d, in the first row of Table 9.1.

Measure the thickness, t, of the trapezoid and record it in Table 9.1.

Use Equation 9.1 to calculate the index of refraction and record your result in
Table 9.1.

Part 2: Ray-tracing Method

Procedure

Place the light source in ray-box mode on a white sheet of paper. Turn the wheel
to select five parallel rays. Shine the rays straight into the convex lens. Place the
mirror on its edge between the ray box and the lens so that it blocks the middle
three rays, leaving only the outside two rays (as in Figure 9.4, but do not put the
trapezoid there yet).

Note: The lens has one flat edge. Place the flat edge on the paper so the lens stands stably
without rocking.

Table 9.1: Results

Part 1: Parallax method

Part 2: Ray-tracing method

Trapezoid

Look

down

Hold pencil

still

Move eye

side to side

Figure 9.3