Points to remember in Physics Part 2

Points to remember in Physics

Part 2

11. Misconception: The Angular momentum of photon is zero.

The statement "the angular momentum of a photon is zero" is not accurate. 

Photons do have angular momentum, which is also known as spin. 

In fact, photons are one of the few elementary particles that have non-zero spin.

The spin of a photon is always equal to 1 in units of Planck's constant h-bar. 

This means that the photon's angular momentum can take on discrete values of ±h-bar and 0, depending on its polarization.

It is important to note that the concept of spin is distinct from orbital angular momentum, which is associated with the motion of a particle around an axis. Since photons are massless particles, they cannot have orbital angular momentum. 

However, they do have spin angular momentum, which is intrinsic to their nature.

12. X_Rays used in crystallography to perform diffraction.

X-rays are commonly used in crystallography to perform diffraction experiments. 

X-ray diffraction is a powerful tool for studying the structures of crystalline solids, including proteins, minerals, and other complex molecules.

In a typical X-ray crystallography experiment, a beam of X-rays is directed at a crystal. 

The X-rays interact with the atoms in the crystal, causing them to scatter in different directions. 

The scattered X-rays interfere with each other, producing a diffraction pattern on a detector.

The diffraction pattern contains information about the arrangement of atoms in the crystal lattice. 

By analyzing the diffraction pattern, researchers can determine the positions of the atoms and the overall structure of the molecule.

X-rays are particularly well-suited for crystallography because their wavelength is similar to the spacing between atoms in a crystal lattice. This means that X-rays can interact with the crystal structure in a way that provides detailed information about the positions of the atoms.

It is worth noting that X-ray crystallography is not the only technique used in structural biology, but it has been a major contributor to our understanding of the structures of biological macromolecules such as proteins and nucleic acids.

13. Bone image is shown on X-rays photography because  X-rays can be absorbed by bones.

X-rays can be absorbed by bone tissue, which makes bones visible on X-ray images. 

When an X-ray beam passes through the body, some of the X-rays are absorbed by the tissue, while others pass through and reach the detector on the other side.

Bones are denser than soft tissue and contain more calcium, which makes them more effective at absorbing X-rays. This means that the X-rays passing through the body are more likely to be absorbed by bones than by other tissues. As a result, bones appear as white areas on X-ray images, while other tissues appear as darker areas.

X-ray imaging is a common diagnostic tool used to evaluate bone fractures, joint dislocations, and other skeletal injuries. It can also be used to detect bone abnormalities, such as bone tumors or osteoporosis.

It is worth noting that X-ray imaging does involve exposure to ionizing radiation, which can potentially increase the risk of cancer. However, the amount of radiation exposure from a typical X-ray is relatively small, and the benefits of the diagnostic information obtained from the X-ray often outweigh the risks. Nevertheless, it is important for healthcare providers to carefully weigh the risks and benefits of any diagnostic test or medical procedure, and to use the lowest possible dose of radiation necessary to obtain the desired information.

14. F=e (V×B) is valid for proton

The formula F=e(V×B) is valid for a proton as well as any other charged particle moving in a magnetic field.

In this formula, F represents the force acting on the charged particle, e is the charge of the particle, V is its velocity, and B is the magnetic field strength.

The vector product V×B represents the direction of the magnetic force acting on the charged particle, which is perpendicular both to the particle's velocity and to the direction of the magnetic field lines.

Therefore, for a proton moving through a magnetic field, this formula can be used to calculate the magnetic force acting on it.

15. Red light photons have the least momentum.

The momentum of a photon is given by its wavelength and frequency through the equation:

p = h/λ = hf/c

where p is the momentum, λ is the wavelength, f is the frequency, h is Planck's constant, and c is the speed of light.

As the wavelength of red light is longer than the wavelengths of other visible colors, it follows that red light photons have less momentum than photons of other visible colors. This can be seen from the equation above, as the momentum is inversely proportional to the wavelength.

Therefore, it is true that red light photons have the least momentum among visible light photons.

16. Angular velocity can not be infinite.

Angular velocity is defined as the rate at which an object rotates or revolves around a fixed axis. It is given by the formula:

ω = Δθ/Δt

where ω is the angular velocity, Δθ is the change in angle, and Δt is the time taken for the change to occur.

It is not possible for the angular velocity to be infinite because that would imply that an object is rotating or revolving around an axis at an infinitely fast rate, which is not physically possible.

In reality, all objects have a maximum angular velocity that they can reach before they become unstable and disintegrate. This maximum velocity depends on the object's properties, such as its mass, shape, and strength, as well as the properties of the material it is made of.

Therefore, it is true that angular velocity cannot be infinite, as it is limited by physical laws and the properties of the object that is rotating.

17. Misconception: Microscope uses shorter wavelengths to reduce diffraction.

This statement is not entirely accurate. In fact, a microscope uses shorter wavelengths of light to increase its resolving power or ability to distinguish between two closely spaced objects. 

This is because the shorter wavelength of light allows the microscope to overcome the diffraction limit, which is the physical limit of the microscope's ability to distinguish between two points that are close together. 

When the wavelength of light is shorter, the microscope can achieve a higher resolution, which is essential for visualizing small structures such as cells and subcellular components.

18. Laser light is uni-directional.

This statement is generally true. Laser light is characterized by its highly directional, collimated, and coherent nature. 

The term "laser" stands for "Light Amplification by Stimulated Emission of Radiation," and it refers to a device that produces a very intense, highly focused beam of light. 

The laser light is produced by the stimulated emission of photons from a medium that has been excited by an external source of energy. 

The photons in the laser beam are all traveling in the same direction, and they are all in phase with each other, meaning that the crests and troughs of the waves are all aligned. 

This coherence and directionality of laser light make it useful for a wide range of applications, including in medicine, telecommunications, and manufacturing. 

However, it is possible to create laser light that is not uni-directional, such as in ring lasers or chaotic lasers, but these are specialized types of lasers with specific purposes.

19. A cycle tyre burst suddenly is an example of the Adiabatic process.

Yes, a cycle tyre bursting suddenly is an example of an adiabatic process. 

An adiabatic process is a thermodynamic process in which there is no exchange of heat between the system and its surroundings. In the case of a cycle tyre bursting suddenly, the air inside the tyre expands rapidly due to an increase in temperature. This sudden expansion of air occurs very quickly, and there is no time for heat to transfer between the air inside the tyre and the surroundings. Therefore, the process is adiabatic.

As the air inside the tyre expands, it does work on the tyre, which causes it to burst. This work is done at the expense of the internal energy of the air, which decreases as a result. The decrease in internal energy is accompanied by a decrease in temperature, which is why the air inside the tyre feels cool to the touch after the tyre bursts.

Thus, a cycle tyre bursting suddenly can be considered an example of an adiabatic process because there is no exchange of heat between the system (the air inside the tyre) and its surroundings during the process.

20. Very hot stars emit blue colour.

Yes, very hot stars emit blue color. 

Stars emit light due to the nuclear reactions that take place in their cores. The temperature of a star's core determines the color of the light it emits. Hotter stars emit more energy and have shorter wavelengths, which correspond to blue or blue-white light. Cooler stars emit less energy and have longer wavelengths, which correspond to red or orange light.

Blue light has a shorter wavelength and higher frequency than red light. When a star is very hot, such as a blue-white O-type star, it emits a lot of high-energy photons, including blue light. These stars have surface temperatures that can exceed 30,000 Kelvin, which is much hotter than the surface of the Sun. 

On the other hand, cooler stars like red dwarfs emit mainly red or orange light, because their surface temperatures are lower than the Sun's. Red dwarfs have surface temperatures that range from about 2,500 to 4,000 Kelvin.

Therefore, the color of a star depends on its temperature, with hotter stars appearing blue or blue-white, and cooler stars appearing red or orange.