Place one of the converging lenses on a sheet of paper and trace its outline. Wi
ID: 1567397 • Letter: P
Question
Place one of the converging lenses on a sheet of paper and trace its outline. Without altering the lens position, arrange the light box to project several parallel rays and move it so that it projects the rays parallel to the axis of symmetry of the lens. Trace the rays. The rays will converge as they leave the lens. Trace the refracted rays and mark the point at which they converge. This is the focal point of the lens. Measure the focal length of this lens (the distance from the focal point to the center of the lens) and record it on your drawing. As with the mirror, trace the curve of one side of tire lens surface on your sheet of paper. Move the curved surface along this tracing and extend the tracing a number of times until it forms a circle. Measure the diameter of the circle and calculate the radius. Record these results on your drawing. Repeat the procedure of part I for the other converging lens. How does the radius of curvature affect the focal length ? Can you determine a relationship between the radius and the focal length? If a lens of focal length 20 mm is required, what radius of curvature should be used? The curvature of a lens does not necessarily need to be the same for both sides. Lenses may be a variety of shapes. The relationship between the focal length, tire index of refraction and the radii is given by the Lens-makers' Equation: 1/f = (n - 1)[1/R_1 + 1/R_2] where: f = the focal length of the lens n = the index of refraction of the lens material R_1 = the radius of curvature of one of the sides R_2 = the radius of curvature of the other side What are the values of R_1 and R_2 for the two bi-convex lenses you used above? Using these values and the Lens-makers' Equation, determine the value of n for the plastic material in the lenses.Explanation / Answer
1. Radius of curvature affect the focal length in way that they are directly proportional i.e. if one increases then other increases. Radius of curvature defines the radius of the sphere from which the lens is taken but focal length is the place where the light after refraction from the lens meet. For a spherical bi-convex lens, radius of curvature R, refractive index n, max thickness t in medium of air, centered at the origin is the intersection of two spheres x^2+y^2+(z-(Rt/2 ))^2=R2=x^2+y^2+(z+(Rt/2))^2 where z is the optic axis.
2. For mirror f = R/2 but it's not the same for the lens. For the lens there is len's maker formula.
3. Can be calculated considering R1 and R2 be the same and there is some refractive index.