PHY101 Solved Current Papers Fall 2021 by Adil Alvi

PHY101 CURRENT PAPERS FALL 2021

Q1. Calculate the energy, in joules, of a photon of green light having a wavelength of 562nm?

Q2. Find the difference between two waves which interfere constructively and destructively?

When two waves occupy the same point, superposition occurs. ... Constructive interference is when two waves superimpose and the resulting wave has a higher amplitude than the previous waves. Destructive interference is when two waves superimpose and cancel each other out, leading to a lower amplitude.

Q3. Similarity and difference of galvanometer and electric motor?

1. Galvanometers and electric motors are both based on the same basic principle of an external magnetic field exerting a force on a current carrying wire. The difference is in how far the device is allowed to move. ...
2. Motors must be able to move freely and rotate through complete 360o turns.

Q4. How does the source make difference of gamma rays and x rays?

The key difference is the source: x-rays are emitted by the electrons outside the nucleus, and gamma rays are emitted by the excited nucleus itself. ... The gamma rays' wavelength is smaller than that of the x-rays'. Gamma-ray photons have the highest energy in the EMR spectrum and their waves have the shortest wavelength.

Q5. Difference between quantum mechanics and classical mechanics?

In classical mechanics, objects exist in a specific place at a specific time. However, in quantum mechanics, objects instead exist in a haze of probability; they have a certain chance of being at point A, another chance of being at point B and so on.

Q6. What will be happen when wavelength is small in interference?

A higher frequency corresponds to a shorter wavelength. Waves of shorter wavelength spread out (diffract) less after passing through the slits, and the short wavelength leads to a smaller angle at which constructive interference (one wavelength path difference between the two waves) will occur.

Q7. What is Alpha decay?

Alpha decay is the nuclear decay process whereby the parent nucleus emits an alpha particle. The alpha particle, structurally equivalent to the nucleus of a helium atom and denoted by the Greek letter α, consists of two protons and two neutrons.

Q8. What is Motion?

In physics, motion is the change in position of an object with respect to its surroundings in a given interval of time.

Q7. What is Black-body radiation?

Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific spectrum of wavelengths, inversely related to intensity that depend only on the body's temperature, which is assumed for the sake of calculations and theory to be uniform and constant

Q8. Difference between reflection and refraction?

Reflection involves a change in direction of waves when they bounce off a barrier. Refraction of waves involves a change in the direction of waves as they pass from one medium to another.

Q9. Magnetic flux and magnetic flux density and when flux is maximum and when it is zero?

Magnetic flux is a measurement of the total magnetic field which passes through a given area. Magnetic flux density (B) is defined as the force acting per unit current per unit length on a wire placed at right angles to the magnetic field. Magnetic flux through a coil is maximum when it is equal to zero. If there is no net charge within a closed surface then flux is zero

Q10. What is fundamental source of electromagnetic radiation?

A moving charge particle is the fundamental source of electromagnetic radiation.

Q11. What is coronavirus?

Coronavirus disease (COVID-19) is an infectious disease caused by the SARS-cov-2 virus.

12) Difference between potential energy and potential difference/

Potential energy, stored energy that depends upon the relative position of various parts of a system while the difference in potential between two points that represents the work involved or the energy released in the transfer of a unit quantity of electricity from one point to the other.

Q13. What is ampere?

The ampere is a measure of the amount of electric charge in motion per unit time

Q14. What is transverse waves and longitudinal waves?

Transverse waves cause the medium to move perpendicular to the direction of the wave. Longitudinal waves cause the medium to move parallel to the direction of the wave.

Q15. What is Greenhouse effect?

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without this atmosphere. Radiative active gases in a planet's atmosphere radiate energy in all directions.

Q13. What is Composition of sun?

Composition: 72% H, 25% He, rest is metals

Q14. Comparison of radio waves and light waves?

Both radio waves and light are electromagnetic waves; their main difference is their frequency. Radio waves are created by the acceleration of electrons in a radio antenna, and light waves are

Q15. Why does reducing the temperature on the surface of cooker help me accelerate the reduction of pressure inside the cooker?

Cooling the surface will cause heat to flow through the metal from the inside wall. Water vapor will condense back to steam on the cooled parts of the inside wall, reducing the pressure.

Q16. Difference between resistance and resistivity?

Resistance is defined as the property of the conductor which opposes the flow of electric current. Resistivity is defined as the resistance offered by the material per unit length for unit crosssection. The SI unit of resistivity is Ohm.

Q17. Did 1/p+1/q=1/f or m=-q/p apply on image which is formed by flat mirror?

Yes, the mirror equation and the magnification equation apply to plane mirrors. A curved mirror is made flat by increasing its radius of curvature without bound, so that its focal length goes to infinity. From 1/p + 1/q = 1/f we have 1/p = -1/q. the magnification is M= -q/p = p/p = 1. The image is right side up and actual size.

Q18. Explain fusion reaction of sun?

In a fusion reaction, two light nuclei merge to form a single heavier nucleus. The process releases energy because the total mass of the resulting single nucleus is less than the mass of the two original nuclei.

Q19. Proton and electron have same wavelength according to de Broglie. Which is faster?

The de Broglie wavelength of a particle is inversely proportional to its momentum p = m v; since a proton is about 1800 times more massive than an electron, its momentum at the same speed is 1800 times that of an electron, and therefore its wavelength 1800 times smaller. The electron has the longer wavelength.

Q20. What is the major problem of specific heat while measuring the temperature of water above 100°c?

If the water boils you are losing information that you need. At boiling the heat is not causing a change in temperature but a change in Phase (liquid to vapor). The heat of fusion (to make ice) for water at 0 °C is approximately 334 joules (79.7 calories) per gram, and the heat of vaporization at 100 °C is about 2,230 joules (533 calories) per gram. So 2,230J/g at 100C are evaporating and leaving no trace.