Optics - Magnification

Question 1

magnification

Answer 1

• The Image that a lens forms does not have to be the same size as the original Object. There are times we’d like our lens to make a larger image, as in a movie projector. There are other times we’d like the image to be smaller than the object, like the images on a piece of film. In these cases, we say the image has been “magnified,” and the process is called “Magnification.”
• If ho stands for the height of the Object, and hi the height of the image, the Magnification ”M” is defined to be how many times bigger the Image is than the object
• If M is larger than 1, it means hi is bigger than ho; the image has been magnified. If M is smaller than 1, then hi is smaller than ho; the image has been decreased, or “minified.”
• If the object is inverted, then the image points downward, below the axis. In that case, hi is negative, which makes M negative as well. A positive M means the image has not been flipped, but is right side up; a negative M means the object has been flipped over or inverted.
• +M = Upright image
• -M = Inverted image
• If you work through the math on a Ray Diagram, you find the magnification depends on whether do or di is bigger. Basically, the farther the image di is from the lens, the bigger the magnification will be. If di is twice as far as do, the magnification will be 2, and so on.
• Often a problem will have you find di or do from the Thin Lens Equation, then have you use them to calculate M. Or, it can ask you to do the opposite thing: knowing hi and ho, you can find do or di, then put them in the Lens Equation.