Question Library

Resonance in an AC circuit occurs when the inductive reactance (XL) is equal to the capacitive reactance (XC). This is because at this point, the two reactances cancel each other out, leaving only the resistance of the circuit. As a result, the impedance of the circuit is minimized.

The stopping potential is the voltage that is required to stop the emitted photoelectrons from reaching the anode. When the frequency of the light is increased, the kinetic energy of the emitted photoelectrons also increases. This means that a higher stopping potential will be required to stop the photoelectrons from reaching the anode.

An intrinsic semiconductor, also called an undoped semiconductor, is a pure semiconductor. In intrinsic semiconductors the number of excited electrons and the number of holes are equal: n = p

\(T_ {^1/_2}\) = 12 days ;V=? \(T_ {^1/_2}\) = \(\frac{0.693}{γ}\) ⇒γ ⇒\(\frac{0.693}{t_{^1/_2}}\) ⇒γ =\(\frac{0.693}{12}\) ⇒γ= 0.05775 \(day^{-1}\)

Nuclear fusion is the process in which lighter nuclei are combined to form heavier ones. Matter lost in this process is converted into energy. The energy produced inside the stars is due to the process of nuclear fusion.

The penetrating power of alpha rays, beta rays, and gamma rays varies greatly. Alpha particles can be blocked by a few pieces of paper. Beta particles pass through paper but are stopped by aluminum foil. Gamma rays are the most difficult to stop and require concrete, lead, or other heavy shielding to block them. Therefore, X = γ-ray; Y = \alpha-particle; Z = \beta-particle

The Bohr model is a model of the atom that describes electrons as orbiting the nucleus in specific energy levels. This model was developed by Niels Bohr in 1913 and it is based on the work of Max Planck and Albert Einstein. The Rutherford model, the Thomson model, and the Dalton model are all older models of the atom that are not as accurate as the Bohr model.

Classical mechanics is a branch of physics that deals with the motion of macroscopic objects. It is based on the principles of Newton's laws of motion and is not considered to be part of elementary modern physics. The other three options, quantum mechanics, special relativity, and nuclear physics, are all considered to be part of elementary modern physics because they deal with the behavior of matter and energy at the atomic and subatomic levels.

As light ray enters a drop of water the light is refracted at the surface and at the end of the drop, it is totally internally reflected in which the reflected light returns to the front surface, where it again undergoes refraction as it moves from water to air. The result of this is a dispersed light of colours of different wavelengths.

The pinhole camera works on the principle of the rectilinear propagation of light. This principle states that light travels in straight lines. When light passes through the tiny hole in a pinhole camera, it forms an inverted image on the opposite side of the camera. The size of the image depends on the distance between the object and the pinhole.

f = 15cm (diverging mirror); u = -35cm(because object is in front of the mirror) v=? ⇒\(\frac{1}{f}\) = \(\frac{1}{v}\) + \(\frac{1}{u}\) ⇒ \(\frac{1}{15}\) = \(\frac{1}{v}\) - \(\frac{1}{35}\) ⇒ \(\frac{1}{15}\) + \(\frac{1}{35}\) = \(\frac{1}{v}\) ⇒ \(\frac{105}{10}\) = \(\frac{1}{v}\) v = \(\frac{105}{10}\) = 10.5cm ∴The image is 10.5cm behind the mirror, since v is positive.

n=1.458, c=\(3.00 \times10^8 ms^-1\) ,\lambdao = 589nm; f=? Speed of light in a medium (v)=\(\frac{c}{n}\) where n is the refractive index of the medium ⇒\lambdan=\(\frac{589}{1.458}\) = 404nm v=f\lambda ⇒f=\(\frac{v}{\lambda}\) =\(\frac{2.06\times10^8}{404\times10^-9}\) \(1nano=10^{-9}\) ∴f=\(5.09\times10^{14}\) Hz

\(n_1\)=1.33; \(n_2\)=1.5; i=40^\circ; r= ? from snell's law: \(n_1\) x sin i=\(n_2\)x sin r ⇒1.33 x sin 40^\circ=1.5 x sin r ⇒sin r = 0.5700 ⇒r = \(sin^{-1}\) (0.5700) ⇒ r = 34.75

A=0.8m; f=16Hz; v=20 \(ms^-1\); k=? v = f\lambda \lambda =1.25m = k= \(\frac{2\pi}{\lambda}\) =\(\frac{2 \times 3.142}{1.25}\) k= 5m ( to 1 s.f)

Infrared waves are used in night vision goggles because they can penetrate the darkness and allow people to see objects that are not visible to the naked eye