Home
Class 12
PHYSICS
Consider the following statement A and B...

Consider the following statement A and B and identify the correct answer
A) When light falls on two polariod sheets having their axes mutually perpendicular it is completely extinguished
B) When polyvinyl alcohol is subjected to a large strain the molecules get oriented parallel to the direction of strain and material becomes double refractive

A

A is false but B is true

B

A is true but B is false

C

Both A and B are true

D

Both A and B are false

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze both statements A and B to determine their correctness. ### Step 1: Analyze Statement A Statement A claims that when light falls on two Polaroid sheets with their axes mutually perpendicular, it is completely extinguished. 1. **Understanding Polaroids**: When unpolarized light (intensity I₀) passes through the first Polaroid, it becomes polarized and its intensity is reduced to half, which is I₀/2. 2. **Second Polaroid**: The second Polaroid is oriented at 90 degrees (mutually perpendicular) to the first. According to Malus's Law, when polarized light passes through a Polaroid that is perpendicular to its polarization direction, the intensity becomes zero. 3. **Conclusion for Statement A**: Therefore, the light is completely extinguished after passing through the second Polaroid. Hence, Statement A is **true**. ### Step 2: Analyze Statement B Statement B states that when polyvinyl alcohol is subjected to a large strain, the molecules get oriented parallel to the direction of strain and the material becomes double refractive. 1. **Understanding Polyvinyl Alcohol**: Polyvinyl alcohol (PVA) is a polymer that can undergo orientation when subjected to mechanical stress. 2. **Effect of Strain**: When a large strain is applied, the long-chain molecules of PVA align in the direction of the strain. This alignment leads to anisotropic properties in the material. 3. **Double Refraction**: Due to this molecular orientation, the material exhibits double refraction, meaning it has different refractive indices along different axes. 4. **Conclusion for Statement B**: Therefore, Statement B is also **true**. ### Final Conclusion Both statements A and B are correct. Thus, the correct answer is that both statements are true.
Promotional Banner

Topper's Solved these Questions

  • WAVES OPTICS

    AAKASH SERIES|Exercise EXERCISE -IA (MORE THAN ONE OPTION)|14 Videos

  • WAVES OPTICS

    AAKASH SERIES|Exercise EXERCISE -IA (MATCHING TYPE QUESTIONS)|6 Videos

  • WAVES OPTICS

    AAKASH SERIES|Exercise EXERCISE -IA (POLARASATION)|29 Videos

  • WAVES

    AAKASH SERIES|Exercise EXERCISE-III (Doppler effect :)|15 Videos

Similar Questions

Explore conceptually related problems

Consider the following statement A and B and identify the correct answer A) Primary waves travels in a medium with speed of light in all directions. B) Secondary waves travels in backward direction only but not with speed of light

Consider the following statement A and B and identify the correct answer A) Electric vector of electromagnetic wave is the light vector that affects the retina of the eye B) In a polarized light the sum of all the components of the vibrations in one direction is eaqul to the sum of all the components of the vibrations perpendicular to that direction

Consider the following statement A and B and identify the correct answer A) Fresnel.s diffraction pattern occurs when the source of light or the screen on which the diffraction pattern is seen or when both are at finite distance from the aperture B) Diffraction light can be used to estimate the helical structure of nucleic acids

Consider the following statement A and B and identify the correct answer A) In the case of narrow source of light coherent sources are obtained by the division of wave front B) Diffraction is due to interference of light from secondary sources of the same wave front whereas interference is due to superposition of two waves derived from the same source.

Consider the following two statements A and B and identify the correct choice in the given answer A : The characteristic X-ray spectrum depends on the nature of the material of the target B : The short wavelength limit of continuous X-ray spectrum varies inversely with the potential difference applied to the X-rays tube

Read the below Statements about the structure of genetic material and identify the correct ones. I. Adenine and guanine are bases that have a double ring structure , cytosine, thymine and uracil are based with a single ring structure . II. An adenine nucleotide from DNA is the same as an adenine nucleotide from RNA , DNA adenine pairs with uracil and RNA adenine pairs with thymine. III. The base pairing that occurs in a double DNA helix and when RNA is synthesised during transcription follows the rule that a purine pairs with a pyrimidine. IV. The two Polynucleotides on a DNA molecule run in opposite directions so that the double helix formed has two strands that are anti-parallel to each other.

Most materials have the refractive index, n gt 1 . So, when a light ray from air enters a naturally occuring material, then by Snell's law, (sin theta_(1))/(sin theta_(2)) = (n_(1))/(n_(2)) , it is understood that the refracted ray bends towards the normal. But it never emerges on the same side of the normal as the incident ray. According to electromagnetism, the refractive index of the medium is given by the relation, n = (c // v) = +- sqrt(epsilon_(r ), mu_(r )) , where c is the speed of the electromagnetic waves in vacuum, v its speed in the medium, epsilon_( r) and mu_( r) are negative, one must choose the negative root of n . Such negative refractive index materials can now be artifically prepared and are called meta-materials. They exhibit significantly different optical behaviour, without violating any physical laws. Since n is negative, it results in a change in the direction of propagation of the refracted light. However, similar to normal materials, the frequency of light remains unchanged upon refraction even in meta-materials. Answer the following questions : Choose the correct statement.

Consider an evacuated cylindrical chamber of height h having rigid conducting plates at the ends and an insulating curved surface as shown in the figure. A number of spherical balls made of a light weight and soft material and coated with a conducting material are placed on the bottom plate. The balls have a radius r lt lt h . Now, a high voltage source (HV) is connected across the conducting plates such that the bottom plate is at +V_0 and the top plate at -V_0 . Due to their conducting surface, the balls will get charged, will become equipotential with the plate and are repelled by it. The balls will eventually collide with the top plate, where the coefficient of restitution can be taken to be zero due to be soft nature of the material of the balls. The electric field in the chamber can be considered to be that of a parallel plate capacitor. Assume that there are no collisions between the balls and the interaction between them is negligible. (Ignore gravity) Which one of the following statements is correct ?

Read the following paragraph and answer the questions given below , Stable equilibrium is of various types . Mechanical equilibrium is achieved when all particles are at rest and total potential energy of the system is minimum . At any stage where particles are at rest but the system is not at stable equilibrium as it can reduce its potential energy by reverting to another position, is called metastable equilibrium . Thermal equilibrium is result from the absence of temperature gradients in the system. Chemical equilibrium is obtained when no further reaction occurs between reacting substances, i.e forward and reverse rates of reaction are equal. When steam with solid iron at high temperature Fe_3O_4(s) and hydrogen gas are produced . But the reaction never goes to completion. This is because as the products are formed the reaction proceeds in reverse direction and when rate of reverse reaction is equal to rate of forward reaction , the concentration of reactants and products become constant and equilibrium is reached. When two reactants (A) and (B) are mixed to give products (C) and (D) the concentration quotient (Q) at initial stage of the reaction

The Betatron was the first important machine for producing high energy electrons. The action of the betatron depends on the same fundamental principle as that of the transformer in which an alternating current applied to a primary coil induces an altermating current usually with higher or lower voltage in the secondary coil. In the betatron secondary coil is replaced by a doughnut shaped vacuum chamber.Electron produced in the doughnut from a hot filament, are given a preliminary acceleration by the application of an electric field having potential difference of 20 kV to 70 kV , when an alternating magnetic field is applied parallel to the axis of the tube, two effects are produced (1) an electromotive force is produced in the electron orbit by the changing magnetic flux that gives an additional energy to the electrons (2) a radial force is produced by the action of magnetic field whose direction is perpendicular to the electron velocity. Which keeps the electron moving in a circular path. Conditions are arranged such that the increasing magnetic field keeps the electron in a circular orbit of constant radius. The mathematical relation between the betatron parameters to ensure the above condition is called BETATRON condition. If the orbit radius of the circular path traced by the electron is R , magnetic field is B , speed of the electron is v , mass of the electron is m , charge on the electron is e and phi is the flux within the orbit of radius R . Then answer the following questions based on the above comprehension. What is the tangential force acting on the electron ?