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The first three spectral lines of H-atom in the Balmer series are given λ1, λ2, λ3 considering the Bohr atomic model, the wavelengths of first and third spectral lines (λ1/λ3) are related by a factor of approximately ‘x’×10–1. The value of x, to the nearest integer, is ________.

Answer: (15) For 1st line \(\begin{array}{l}\frac{1}{\lambda _{1}}=Rz^{2}(\frac{1}{2^{2}}-\frac{1}{3^{2}})\end{array} \) \(\begin{array}{l}\frac{1}{\lambda _{1}}=Rz^{2}(\frac{5}{36})\end{array} \) ———(1) For 3rd line \(\begin{array}{l}\frac{1}{\lambda _{3}}=Rz^{2}(\frac{1}{2^{2}}-\frac{1}{5^{2}})\end{array} \) \(\begin{array}{l}\frac{1}{\lambda _{3}}=Rz^{2}(\frac{21}{100})\end{array}... View Article

The angle of deviation through a prism is minimum when (A) Incident ray and emergent ray are symmetric to the prism (B) The refracted ray inside the prism becomes parallel to its base (C) Angle of incidence is equal to that of the angle of emergence (D) When the angle of emergence is double the angle of incidence Choose the correct answer from the options given below: a. Only statement (D) is true b. Statements (A), (B) and (C) are true c. Statements (B) and (C) are true d. Only statement (A) and (B) are true

  Answer: (b) Deviation is minimum in prism when, i = e, r1=r2 and ray inside prism is parallel to... View Article

For changing the capacitance of a given parallel plate capacitor, a dielectric material of dielectric constant K is used, which has the same area as the plates of the capacitor. The thickness of the dielectric slab is (¾) d, where ‘d’ is the separation between the plates of parallel plate capacitors. The new capacitance (C’) in terms of original capacitance (C0) is given by the following relation:

a.\(\begin{array}{l}C’=\frac{4K}{K+3}C_{0}\end{array} \) b. \(\begin{array}{l}C’=\frac{4}{3+K}C_{0}\end{array} \) c. \(\begin{array}{l}C’=\frac{3+K}{4K}C_{0}\end{array} \) d. \(\begin{array}{l}C’=\frac{4+K}{3}C_{0}\end{array} \) Answer: (a) \(\begin{array}{l}C_{0}=\frac{\epsilon _{0}A}{d}\end{array} \) C1 and C2 are... View Article

A conducting bar of length L is free to slide on two parallel conducting rails as shown in the figure. Two resistors R1 and R2 are connected across the ends of the rails. There is a uniform magnetic field → B pointing into the page. An external agent pulls the bar to the left at a constant speed v. The correct statement about the directions of induced currents I1 and I2 flowing through R1 and R2 respectively is : a. I1 is in the clockwise direction and I2 is in the anticlockwise direction b. Both I1 and I2 are in a clockwise direction c. I1 is in the anticlockwise direction and I2 is in a clockwise direction d. Both I1 and I2 are in the anticlockwise direction

  Answer: (a) When the bar slides, the area of loop 1 decreases and that of loop 2 increases. Magnetic... View Article

A conducting wire of length ‘l’, area of cross-section A and electric resistivity ρ is connected between the terminals of a battery. A potential difference V is developed between its ends, causing an electric current. If the length of the wire of the same material is doubled and the area of cross-section is halved, the resultant current would be:

a. \(\begin{array}{l}\frac{1}{4}\frac{\rho l}{VA}\end{array} \) b. \(\begin{array}{l}\frac{3}{4}\frac{VA}{\rho l}\end{array} \) c. \(\begin{array}{l}4\frac{VA}{\rho l}\end{array} \) d. \(\begin{array}{l}\frac{1}{4}\frac{VA}{\rho l}\end{array} \) Answer: (d) We know... View Article