kelas sains smp athirah baruga: LIGHT, MIRRORS, AND LENSES

What Is Light?

What can you see in a dark room with no windows or lights?
You cannot see anything until you turn on the lights or open the door to let in light from outside the room. Most objects around you are not light sources. For these objects to be seen, light from a light source bounces off the objects and into your eyes.

The figure below shows how this works. The process of light hitting an object and bouncing off is called reflection. You can read the words on this page because of reflection. Light from a source reflects from the page and into your eyes. However, not all light rays reflected from the page go to your eyes. Light rays reflect in many directions.

In the Quran, Surah Yunus, verse 5,

God Who makes the sun shine and the moon shine.

This verse explains the physical nature of light: the sun emits its own light (dhiya'), while the moon reflects light (nur). From a scientific perspective, this verse is consistent with the concept that the Sun produces its own light through energy generation, while the Moon shines because it reflects sunlight.

Light is a form of energy that travels in the form of waves. Light allows us to see objects.
Light travels in a straight line. Light moves very fast, Its about 300,000 km/s.

Properties of Light

Light travels in a straight line
→ Example: shadows form because light cannot bend around objects.

Light can be reflected
→ When light bounces off a surface.

Light can be refracted
→ When light bends as it passes from one medium to another (air to water, air to glass).

Light can be absorbed
→ Dark objects absorb more light.

Light can be dispersed
→ White light splits into colors (rainbow).

pic taken from : https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.harapanrakyat.com%2F2021%2F09%2Fpengertian-dispersi-cahaya%2F&psig=AOvVaw0QuKR3AiBBIA-2SDAMePrx&ust=1691704802226000&source=images&cd=vfe&opi=89978449&ved=2ahUKEwiBnNfPydCAAxUkoekKHcvEBMEQ3YkBegQIABAO

Light can be Interferenced

→ it happen when bright and dark patterns appear when two light waves overlap.

Light can be diffracted

→ it happen when light spreads out after passing through a narrow slit.

MIRRORS

Mirrors reflect light. There are three main types of mirrors:

1. Plane Mirror

Plane mirros is a flat mirror. Produces an image that is: Same size, Upright, Virtual (cannot be projected on screen), Laterally inverted (left appears right)

Example: bathroom mirror.

How is an image formed in a plane mirror ?

The image in a plane mirror seems to be behind the mirror because of the way your brain understands the light rays that enter your eyes. When the light rays bounce off the mirror’s surface, your brain thinks they followed the path shown by the dashed lines in the figure below. Your brain thinks light rays travel in straight lines without changing direction. This makes reflected light rays look like they are coming from behind the mirror. The image also looks like it is the same distance behind the mirror as the person is in front of the mirror.