Zhikai Thin lenses

# Zhikai Thin lenses - PC1221 Lab Report The Force of...

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PC1221 Lab Report: The Force of Gravity|| ||Wang Zhikai|| ||A0080959N|| ||Group A1|| PC1221 Lab Report: The Force of Gravity|| ||Wang Zhikai|| ||A0080959N|| ||Group A1|| 1 Objectives To determine an experimental value for the gravitational acceleration g due to the Earth’s gravitational pull via the motion of a cart rolling down an inclined track. To evaluate the extent to which the total mechanical energy, which is the sum of kinetic energy plus gravitation potential energy, is conserved. 2 Introduction When light rays parallel to the optical axis are incident upon a converging lens, the rays are brought together at the focal point of the lens. The distance from the centre of the lens to the focal point is called the focal length of the lens. This quantity is positive for a converging lens. When the same light rays are incident upon a diverging lens, the rays diverge as they leave the lens. However, when we trace the path of the outgoing rays backward, they appear to have emerged from a point between the lens and the light source, also known as the focal point of the lens. The focal length of a diverging lens is a negative quantity. Diverging lens can only form virtual images, where light does not actually pass through the points at which the image is formed and thus, the image cannot be focused on a screen. Converging lens form either real or virtual images depending on the distance the object is from the lens. When the object is further from the lens than its focal length, a real image is formed. When the object is nearer to the lens than the focal length, a virtual image is formed. After being formed, virtual images act as the object for another lens system to form a real image. When an image is formed, the distance from an object to the lens is the object distance, d o and the distance of an image from the lens is d i . d o , d i and the focal length of the lens f are related by the equation . When two lenses are placed in contact to one another, their individual focal lengths and their effective focal length are related by the equation . The aim of the experiment is to determine the focal length of a converging lens, a diverging lens and a combination of a converging and diverging lens by projecting real images of an object through the lens onto a screen. 3 Methodology Part A: Focal Length of Converging Lens We placed the converging lens on the optical bench and used the lamp as the object. We recorded the manufactured focal length of the converging lens as f A in Data Table 1. We then placed the light source and the screen on the optical bench 100cm apart and placed the converging lens between them. We started out by placing the lens close to the screen and began sliding the lens away from the screen until a sharp image of the object is formed. We measured the object and the image distance as d o and d i in Data Table 1. We then moved the lens close to the object and repeated the previous steps until the image was in focus and measured this different set of object and image distances. We then repeated the previous steps, but with different distances between the light source and the screen,

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## This note was uploaded on 01/09/2012 for the course ELECTRICAL 1221 taught by Professor Tan during the Spring '11 term at National University of Singapore.

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Zhikai Thin lenses - PC1221 Lab Report The Force of...

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