Physics Answers

At a distance of 5 m from a point sound source, the sound intensity level is 110 dB. At what distance is the intensity level 95dB?

Show that the de Broglie wavelength of a particle in a one dimensional box in the first
excited state is equal to the length of the box.

A convex mirror has a focal length of -27 cm. What is the position of the image when the object is placed 9 cm in front of the mirror?

How far (in cm) would a light travel through diamond in 1 micro sec ? The index of refraction of diamond is 2.419.

A piece of newspaper is underneath a slab of crown glass that is 2.54 cm thick. When viewed from above, how thick does the slab appear to be ? (ncrown glass = 1.523)

Light is reflected from a glass coffee table. When the angle of incidence is 60.2 degrees, the reflected light is completely polarized parallel to the surface of the glass. What is the index of refraction of the glass?

what would the speed of an observer be if a red(4.688x10^14 Hz) traffic light appeared green (5.5555x10^14 Hz) to the observer ?

A cannon from the Napoleonic wars was able to launch cannon balls at a velocity of 540 m s–1. The cannon is fired at the top of a cliff with the barrel in the horizontal position.
(a) Neglecting air resistance, what is the range of the cannon ball, to the point where it hits the water 100 m below?
(4 marks)
(b) Calculate the initial horizontal component of the momentum of the cannon ball, if it has a mass of 5.44 kg. (2 marks)
(c) If the cannon has a mass of 5000 kg and is on a trolley on the horizontal surface, what is its initial recoil velocity?
(2 marks)

(a) Calculate ∆H and ∆S, the enthalpy and entropy changes, respectively,
when one mole of copper (initially at 500 K) is brought into thermal equi-
librium with a thermal reservoir at 400 K. Consider one mole of copper
and the thermal reservoir to form an isolated system. [Hints: 1. Thermal
reservoirs are chambers which are always maintained at the same temper-
ature irrespective of the temperatures of the objects in contact with it, 2.
S is an extensive state function.]
(b) Comment whether the process is reversible or irreversible.

(a) Consider an isolated system that contains two pieces of copper sepa-
rated by an (internal) insulating wall. Initially, the first piece is at 500K
and the second is at 300K. Calculate the entropy change in the sys-
tem when the insulating wall is removed; assume that each piece has
half a mole of copper in it. Given: Specific heat capacity of Cu is
CP = 22.6JK−1mol−1
.