Ray Optics in Physics Class 12

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6 Questions

What phenomenon describes how light travels in straight lines from a source to an observer?


What happens when light strikes a smooth surface at a glancing angle?

It reflects away from the surface at the same angle

What is the term for the process where light changes speed and direction continuously as it passes through a medium with varying density?


Which of the following is an example of precise reflection?

Mirror reflections

What happens to the speed of light when it moves from air to glass?

It slows down

In refraction, why does the reflected ray bend rather than go directly to the eye?

Due to change in speed and direction when passing through different media

Study Notes

Ray Optics in Physics Class 12

Ray optics forms a crucial aspect of the Physics curriculum in Class 12, covering various topics related to light propagation and properties. Here, we delve into some of the main elements of ray optics:

Light Propagation

In ray optics, we consider how light travels in straight lines from a source to an observer, reflecting off surfaces before reaching our eyes. This allows us to describe what happens when light interacts with objects—whether they diffuse light (scattering), absorb light, or transmit it without any change in direction.


When light strikes a smooth surface at a glancing angle, it rebounds away from the surface while preserving its path at the same angle. In instances where the surface is rougher, the reflected beam spreads out to form scattered light. Mirror reflections are examples of precise reflection, whereas diffused light reflects less accurately, creating a wider cone of light.


Light passing through a medium with varying density changes speed and direction continuously; this process is called refraction. When light moves from air to glass, for example, it slows down and turns towards the normal line (the imaginary line drawn vertically through the point of contact). This causes the reflected ray to bend rather than go directly to the eye, forming images inside the lens.

Image Formation

If light enters a transparent material whose index of refraction varies along a curved trajectory, it begins to focus into a tiny spot, increasing in intensity (a phenomenon known as converging). Depending on the shape of the lens (convex or concave), it can either focus light to a point or away from it, causing divergence instead of convergence.

These core ideas forge the basis of many experiments you could perform in your studies, including those found in optics laboratories, which explore how we see things under various conditions (like viewing distant stars or near objects) and create pictures using magnifying glasses or microscope objectives.

Explore the fundamental concepts of ray optics in Physics Class 12, including light propagation, reflection, refraction, and image formation. Learn about how light interacts with different surfaces and mediums, forming images and affecting our perception of the world around us.

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