In this Physics video lecture for IIT JEE mains, we will talk on the topic ray optics. The topics covered in the above physics video are;

• Ray optics
• Few important terms
• Sign convention

So let’s begin with ray optics in physics. Optics is the study of nature of light under various conditions. Talking about the nature of light, the first theory was given by Newton. This theory is called Newton’s corpuscular theory. According to this theory, light is made up of small corpuscles of energy which travels in a certain media and the size of the corpuscles for different colours. Using this theory, he could explain some phenomenon like reflection and refraction. But after Thomas Young, who gave the first experiment on interference. He told that light is a wave and not corpuscles. After a long time, the scientists believed on what Thomson said. After that, there was de Broglie’s hypothesis.  We know in iit jee physics that light travels in a straight line. The speed of light was found by many scientists and the Maxwell found the speed of light with the help of electromagnetic wave theory. Light is just like an electromagnetic wave pulse and has a particular length. It moves in a straight line. Further, we have discussed a few important terms. They are;

• Mirror: It consists of a glass polished with silver and reflects the light ray. The rays always come from the object.
• Image: It is formed when rays are reflected from the mirror. In the above video, the image formed is a virtual image. The mirror always creates a virtual image for real object and gives a real image for the virtual object.
• Object: It can be anything that is put in front of the mirror. We see the object because the light surrounding the object and reflects enters our eyes. An image is formed in the retina of the eye.

The last topic of physics for iit jee video discussed is signed convention. The direction from which the rays propagate after the reflection is positive and the opposite direction is always –ve x-axis. The axis above it is always +ve y-axis and below it is always is –ve y-axis.