Focal Length of Lenses Lab - University Physics Ii Essay Example
Focal Length of Lenses
Date Lab Conducted: June 19, 2012 Date Due: June 25, 2012 Date Submitted: June 25, 2012
Objectives:
1. To demonstrate that converging lenses form real images while diverging lenses form virtual images.
2. To determine the equivalent focal length of two joined lenses using their individual focal lengths.
3. To measure the focal length of diverging lens by combining it with a converging lens and forming a real image.
List of Apparatus:
- Optical bench containing clamps for lenses and a screen - White screen upon which to project images
- Lap with a geometric object painted upon its face to serve as an illuminate object
- Three lenses: A, B, and C with focal lengths of approximately +30cm, +10cm, and -30cm
- Meter stick
- Masking tape
Theory: Lenses are transparent devices made of glass or plastic and have at least one curved surface. They work by refracting, or bending, light rays passing through them. Parallel waves are caused to either converge or diverge.
Convex lenses have surfaces which bulge outwards in the center. This shape converges light by bending the light rays inward and causing them to intersect at a point just beyond the lens known as the focal point. The distance from the center of the lens to the focal point is the focal length and is a positive number for converging lenses.
Concave lens have an outer surfaces curving inward forming a shallow cavity. This shape diverges light by bending the light rays outward. By tracing these light rays backwards and treating them as linear, unbent waves, a focal point can be found in front of the lens. The distance from this point to the center of the lens is the focal length and it is a negative number for diverging lenses.
Lenses form two types of images – real and virtual. Real images can be focused on a screen and result from light waves passing through the points in space in which the image is formed. Virtual
Date Lab Conducted: June 19, 2012 Date Due: June 25, 2012 Date Submitted: June 25, 2012
Objectives:
1. To demonstrate that converging lenses form real images while diverging lenses form virtual images.
2. To determine the equivalent focal length of two joined lenses using their individual focal lengths.
3. To measure the focal length of diverging lens by combining it with a converging lens and forming a real image.
List of Apparatus:
- Optical bench containing clamps for lenses and a screen - White screen upon which to project images
- Lap with a geometric object painted upon its face to serve as an illuminate object
- Three lenses: A, B, and C with focal lengths of approximately +30cm, +10cm, and -30cm
- Meter stick
- Masking tape
Theory: Lenses are transparent devices made of glass or plastic and have at least one curved surface. They work by refracting, or bending, light rays passing through them. Parallel waves are caused to either converge or diverge.
Convex lenses have surfaces which bulge outwards in the center. This shape converges light by bending the light rays inward and causing them to intersect at a point just beyond the lens known as the focal point. The distance from the center of the lens to the focal point is the focal length and is a positive number for converging lenses.
Concave lens have an outer surfaces curving inward forming a shallow cavity. This shape diverges light by bending the light rays outward. By tracing these light rays backwards and treating them as linear, unbent waves, a focal point can be found in front of the lens. The distance from this point to the center of the lens is the focal length and it is a negative number for diverging lenses.
Lenses form two types of images – real and virtual. Real images can be focused on a screen and result from light waves passing through the points in space in which the image is formed. Virtual