Physics Lenses and Geometric Optics

Emma L.

Physics 132 Lab

Lab 1: Lenses and Geometric Optics

Abstract:

In this lab, the overarching theme was measuring different properties of light using geometric optics. In part 1 of the experiment, we tested the law of reflection where the angle of the ray of incidence is equal to the ray of reflection (θi = θr) and Snell’s Law of Refraction (nairsin(θair) = nwatersin(θwater)) in two different mediums: air and water. In part 2, we calculated focal lengths of converging lenses using the magnification (m = -hi/h = si/s) and thin lens (1/si + 1/s = 1/f) equations. In the last part of the experiment, we measured combined focal length for diverging lenses using the thin lens equation again to verify that fc has to be less than |fd| in order to get a clear image. All values relating to length were converted into millimeters.

Lab Questions:

1.

Law of Reflection: θ1 = θ2

Tank 1: 38° = 38°

Tank 2: 35° = 35°

Snell’s Law:

Nairsin(θ1) = Nwatersin(θ3)

1.00sin(38°) = Nwatersin(29°)

0.615 = Nwatersin(29°)

Nwater = 1.27 (experimental value), 1.33 (actual value)

2. The focal length was 7.57 cm, and the type of lens used was a converging lens. This could be deduced by how the light rays converged together at one point on the other side of the lens as opposed to a diverging lens where the light rays would separate away from each other and only create a virtual image from the reflected light rays.

3.

1/s + 1/si = 1/f

Trial 1: 1/184 + 1/196 = 1/f , f = 94.9mm

-184/196 = 16/23

Trial 2: 1/358 + 1/147 = 1/f, f = 104.2mm

-358/147 = 35/23

Trial 3: 1/130 + 1/260 = 1/f, f = 86.6mm

-130/260 = 11/23

Trial 4: 1/145 + 1/300 = 1/f, f = 97.76mm

-145/300 = 13/23

4.

1/300 + 1/150 = 1/100

* = 0.01

5. The image is larger than the object and it is upright. Naturally, converging lenses will create an image that is real, inverted, and reduced in size. However, once the object comes in front of...