# Property of Light: Refraction & Angle of Bending

• thecosmos123456
In summary, classical wave optics is all about understanding how light behaves when it interacts with material.
thecosmos123456
the basic property of light is that ,it travels in a straight line but what causes it to travel in a straight line .in refraction of light ,what causes the refracted ray to bend towards the normal ,i am aware that it is related to velocity n material of medium but how does it influence the angle of refraction

This is what classical wave optics is all about.

These behaviors of light can be calculated from first principles using the wave equation derived from Maxwell's laws of electricity and magnetism. The Huygens wavelet model is an easier way of getting an intuitive understanding of what's going on here (google for "Huygens refraction", and pay particular attention to the images).

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If nothing interacts with the photon, conservation of momentum tells us it will travel (approximately) in a straight line.

When light does interact with a material, like a block of glass, the light bends because it travels more slowly in the glass. The direction the light travels is determined by the phase front (the line of peak amplitude) of the light wave. (a plane wave is a stream of parallel phase fronts). The light will always travel forward, perpendicular to that line, but if one part of that beam is inside glass (say, at the interface), then that part of the phase front moves more slowly than the part that's still in air, steering the light beam accordingly.

Of course, even in the vacuum of space, light doesn't quite travel in a straight line.
Due to its wave nature, light diffracts, or spreads out.
As one example, if you pointed a typical laser at the moon, its light would spread out so much that by the time it reached the moon, it would cover most of its surface. With better engineering, we can make that spot size smaller, but not to the point of having the beam be the same width as when it left the laser.

thecosmos123456 said:
the basic property of light is that ,it travels in a straight line
No, light follows a path of stationary optical length. This is related to the index of refraction by integration of the refractive index along the path and known as Fermat's principle. Snell's law of refraction (the one which describes how light is refracted between two media) follows directly from this principle.

jfizzix said:
If nothing interacts with the photon, conservation of momentum tells us it will travel (approximately) in a straight line.

Nothing wrong with the rest of your post... But introducing the word "photon" into this topic in this way can only mislead. @thecosmos123456 , if you can forget that you ever heard the word "photon" until you've thoroughly nailed the classical behavior of light, you'll be better off.

## 1. What is the property of light?

The property of light refers to the characteristics or behaviors of light, such as reflection, refraction, and absorption.

## 2. What is refraction?

Refraction is the change in direction of a light wave when it passes through a medium with a different optical density, such as air to water. This change in direction is caused by the difference in speed of light in the two mediums.

## 3. How does refraction affect the angle of light?

When light passes through a medium with a different optical density, it changes speed and direction, causing the angle of the light to bend. This bending is known as the angle of refraction and is determined by the angle of incidence and the refractive index of the medium.

## 4. What is the angle of incidence?

The angle of incidence is the angle between the incident ray of light and the normal (perpendicular) line to the surface of the medium. It is measured from the direction of the incident ray to the normal line.

## 5. How is the angle of bending calculated during refraction?

The angle of bending, also known as the angle of refraction, is calculated using Snell's law, which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the speeds of light in the two mediums. This can be represented by the equation: n1sinθ1 = n2sinθ2, where n1 and n2 are the refractive indexes of the two mediums and θ1 and θ2 are the angles of incidence and refraction, respectively.

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