Kelebihan Solat Dhuha

Kelebihan Solat Dhuha

Monday, 21 May 2012

Cermin dan Kanta (Ulangkaji)

Flat Mirrors (also called plane mirrors)

An object viewed using a flat mirror appears to be located behind the mirror, because to the observer the diverging rays from the source appear to come from behind the mirror.

The images reflected in flat mirrors have the following properties:

The image distance q behind the mirror equals the object distance p from the mirror

The image height h’ equals the object height so that the lateral magnification 

The image has an apparent left-right reversal

The image is virtual, not real!

Real Image where the light ray actually come to a focus you can actually see the object projected on a screen placed at that location

Virtual Image no light rays actually come directly from a virtual image, they just appear to the eye to do so. (When you see yourself in the mirror, are you actually located behind it as you appear?)

Images Formed by Spherical Mirrors

Spherical Mirror:

Principle Axis: OCIV

Center of Curvature C

Radius of Curvature R

Light rays converge to a real image at image point  I

Where is the image formed? What is its height? Draw two rays: one hitting V and the other passing through C:

. We give this location a special name & designation : the focal point . With this designation we can re-write the concave spherical mirror equation as: 

Note, however, that truly spherical mirrors do not bring all rays to focus at the same location!

Spherical Aberration  this is the problem the Hubble Space Telescope had when first launched.

Convex Mirrors (diverging mirrors) and Sign Conventions

Is the entry for Image location q correct?

Thin Lenses

Note: a convex-concave lenses is sometimes referred to as a meniscus. It is the shape used for most eyeglasses.

Using the same sign convention for thin lenses:

Same as for mirrors!

(This is the thin lens equation)

Multiple Lenses

This is more complicated, but straightforward if you follow these rules:

  1. Do the first lens as if the others weren’t there.

  1. Use the image formed by this lens as the object of the next lens

  1. Repeat this process for all the lenses in the system

  1. The total magnification is just the product of the individual                                                                magnifications of  each lens.

Microscope: Object very close to F0 makes a real inverted larger image. 
This image is then viewed & magnified further using the eyepiece.

Telescope: Object near infinity forms a real inverted smaller image near the focal point. 
Eyepiece is used to magnify this image.

The angular magnification (how much bigger it looks) is just To get different magnifications, just change eyepieces!

Most large telescopes use a concave mirror instead of a lens to form the image.

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