# Light: Refraction, Diffraction, Slits, and Energy Law.

• Prannoy Mehta
In summary, the conversation discusses various aspects of light, including refraction, the effects of changing magnetic fields, the amplitude of light, and energy conservation. The participants also bring up questions about the behavior of light in different scenarios.
Prannoy Mehta
Q1. I do not understand why the light has to bend inorder to undergo refraction. My teachers have explained me that, light bends due to the change in velocity. If I change the velocity of a car by half it's original value, I don't find the cars path changing. It does not seem to make sense to me. Why does the light bend?

Q2. Can light be effected by changing magnetic field.

Q3. What do you mean by amplitude of light? In the wave nature of light. Does it have to do with the magnitutes of the max. Electric field and max. Magnetic field?

Q4. Applying energy conservation in the wave nature of light. Suppose I take two really small areas. If I have a light beam with it's electric field and magnetic field at their maximum let that energy be k. After a time t/4 seconds (t being equal to 1/f, where f is the frequency of light) If I try to find the energy using the classical energy density formulas as earlier, I will get 0. I know I am missing something. What is it ?

Q5. If I have an apparatus, and a magical instruments which are very accurate. If I have thick slits (Thick enough to be 1000 times the thickness of light. If the slits are made of conductors (Assuming their atomic sizes are very very very small). If I pass a light through these slits, with distance between the slits being less then the amplitude of the electric field component of light. What will happen?

I am sorry for the grammatical errors. Thank you for all the help and support.

Q1. Car is not wave. When a beam of light is in oblique incidence on to an interface between different medium, the wavelength changes upon traversing it. The propagation direction must bend in order so that on a wavefront which partially lies in the first and second medium, the wavefront part in the first medium must still be in phase with the wavefront part in the second medium.

Q2. No

Q3. In most cases, the amplitude of electric field.

Q4. The energy for a stationary wave is infinite. You may have forgotten to integrate.

Q5.
Prannoy Mehta said:
distance between the slits being less then the amplitude of the electric field
You cannot compare distance with E field amplitude, they correspond to different physical quantities.

Q1. It makes sense when you look at it in that manner. In the text I am currently referring it says 'that the phase difference between two light waves can change if the waves travel through different materials having different indexes of refraction.' What does this statement imply. There was this question regarding the double slit experiment which is quite famous, keeping a material of a good refractive index (A plastic slab, of 1.5 is given as an example question) on one of the slits. It moves the fringe positions.

Q2. Thank you. :)

Q3. Thank you. :)

Q4. I was referring to the energy density at any point. I am sorry for the confusion. Taking the strips of the magnetic and electric energy at their maximum and at their minimum. They do not seem to be equal. This raised a question in my mind, the answer which you just gave, can we equate planks equation to that of the sum of energy densities (Magnetic and Electric) * Volume (Volume of the segment I have chosen)/

Q5. Thank you, a very silly question indeed.

## 1. What is refraction?

Refraction is the bending of light as it passes through different mediums, such as air, water, or glass. This is caused by a change in the speed of light as it moves from one medium to another.

## 2. How does diffraction occur?

Diffraction is the bending of light as it passes through a narrow opening or around an obstacle. This occurs when the wavelength of light is comparable to the size of the opening or obstacle.

## 3. What is the significance of slits in relation to light?

Slits are used to create interference patterns in light. When light passes through a narrow slit, it diffracts and creates a pattern of light and dark bands. This helps scientists study the properties of light, such as wavelength and frequency.

## 4. What is the energy law of light?

The energy law of light, also known as the law of conservation of energy, states that energy cannot be created or destroyed, but can only be transformed from one form to another. This applies to light as it can be transformed into different types of energy, such as heat or electrical energy.

## 5. How does light interact with matter?

Light can interact with matter in three main ways: reflection, refraction, and absorption. Reflection occurs when light bounces off a surface, refraction occurs when light passes through a medium, and absorption occurs when light is absorbed by matter, converting it into another form of energy.

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