. January 2019

Hydrogen (Like) Atom

Q- The first three energy levels of the fictitious element X are E1 = -3.8 eV, E2 = -1.7 eV, and E3 = -1.2 eV. Element X has one electron in the ground state.

(a) What is the ionization energy of element X?

(b) Calculate the (i) shortest and (ii) next-shortest wavelengths observed in the absorpti…

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Ray Optics: Refraction

Q- An opaque container is 15 cm deep. It contains only a single coin. When looking into the container at a viewing angle of 50o relative to the vertical side of the container, you see nothing on the bottom. When the container is filled with water, you see the coin (from the same viewing angle) on th…

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Newton's Laws: Friction

Q- A box of mass M placed on a table is connected to a hanging mass m by a string passing over a frictionless pulley as in the figure. If the box has mass of 1 kg, the coefficient of friction between the box and table surface is 0.3 and the box slides on the table at constant speed, what is the weig…

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Sound: Intensity and Loudness

Q- A loudspeaker emits a power of 100 W and can be considered as appoint source. Find the sound intensity and sound level in dB at a distance of 10 m from the speaker. How close would you have to be to the speaker for the sound level to be at the threshold of pain (120 dB)?  (The threshold of hearin…

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Q- 15 kg of air in a piston cylinder device is heated inside the cylinder from 250C to 750C by passing current through a resistance heater inside the cylinder. The pressure inside the cylinder is kept constant at 2 bar during the process and the heat loss of 50 kJ occurs. Determine the electrical en…

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