Physics II Final

Dr. Romashets, Lamar University PHYS 1402

turning fork vibrating at 300 Hz is placed in a tank of water.
(a) Find the frequency and wavelength of the sound wave in the water.
(b) Find the frequency and wavelength of the sound wave produced in the air above the
tank by the vibration of the water surface.
* Speed of sound wave in air: v = 343 m/s
* Speed of sound wave in water: v = 1484 m/s

a. Answer: 300 Hz, 4.95 m

b. [Answer: 300 Hz, 1.14 m]

A two-source (S1 and S2) interference experiment of a
certain light is performed. From P to S1 is 2000nm and from P to S2 is 110nm. For following wavelengths, will
you get (1) constructive interference, (2) destructive
interference, or (3) neither constructive nor destructive
interference at point P?

a) 100nm

b) 450nm

c) 600nm

d) 700nm

(a) 100 nm [Answer: constructive]
(b) 450 nm [Answer: constructive]
(c) 600 nm [Answer: destructive]
(d) 700 nm [Answer: neither]

A two-source interference experiment of light with frequency of 1x 1015 Hz is
performed in vacuum. For following path differences, will you get (1) constructive
interference, (2) destructive interference, or (3) neither constructive nor constructive
interference?
a) 450 nm

b) 600 nm

c) 800 nm

d) 900 nm

a) 450 nm [Answer: destructive]
b) 600 nm [Answer: constructive]
c) 800 nm [Answer: neither]
d) 900 nm [Answer: constructive]

Monochromatic light passes through two narrow slits and forms an interference pattern on a screen.

(a) If the wavelength of the light increases, will the distance between
maxima increase, decrease or remain the same?

(b) If the slit of separation is 0.25 mm, the screen is 1.5 m away from the slits, and light of wavelength 550 nm is used, what is the distance from the center of the central maximum to the third-order maximum?

(c) What if the wavelength is 680 nm?

[Answer: (a) increase; (b) 0.99 cm; (c) 1.2 cm

In a single-slit experiment performed in vacuum, a Helium-neon light (f = 4.74 x 1014 Hz) is sent through a 0.300-mm-wide single slit. What is the width of the central maximum on a screen 1.00 m from the slit?

[Answer: 4.22 mm]

How many maxima appear when monochromatic light of wavelength 560 nm
illuminates a diffraction grating that has 10,000 lines/cm, and what are their order numbers?

[Answer: 3]

Find the angles of the blue (λ = 420 nm) and red ((λ = 680 nm) components of the first- and second-order maxima in a pattern produced by a diffraction grating with 7500 lines/cm.

[Answer: for blue, 18.4o and 39.2o; for red, 30.7o and impossible]

Two people stand 8.0 m apart and 3.0 m away from a large plane mirror in a dark room. At what angle of incidence should one of then shine a flashlight on the mirror so that the reflected beam directly strikes the other person?

[Answer: 53.1o]

The laser used in cornea surgery is ultraviolet light with a wavelength of 193 nm in air. The refractive index of the cornea is 1.376. What are wavelength and frequency of the light in the cornea?

[Answer: (a) 140 nm; (b) 1.55 x 1015 Hz]

A beam of light enters water from air.

(a) Will the angle of refraction be (1) greater than, (2) equal to, or (3) less than the angle of incidence?

(b) if the angle of incidence is 50o, find the angle of refraction.

[Answer: (a) less than; (b) 35.2o]

A beam of light enters water from air.

(a) Will the angle of refraction be (1) greater than, (2) equal to, or (3) less than the angle of incidence?

(b) if the angle of incidence is 35.2o, find the angle of refraction.

[Answer: (b) 25.6o]

A beam of light in air is incident on the surface of a slab of fused quartz

(n = 1.458). Part of the beam is transmitted into the quartz at an angle of refraction of 30o relative to the normal, and part is reflected.

(a) What is the angle of reflection?

(b) What is the angle between the reflected ray and refracted ray?

[Answer: (a) 46.8o, (b) 103.2o]

A beam of light is incident from air onto a flat piece of polystyrene

(n = 1.5916) at an angle of 45o relative to the surface. What angle does the refracted ray make with the plane of the surface?

[Answer: 63.6o]

A swimming pool filled with water and the width is 5.50 meters. The bottom edge of the pool is just visible at an angle of 14 degrees above the horizontal.

a) Calculate the depth of the pool.

b) if you look down at the bottom of the pool from above what is the apparent
depth of the pool?

[Answer: (a) 5.17 m, (b) 1.37 m]

(a) For total internal reflection to occur, should the light be directed from (1) air to water or (2) water to air?

(b) What is the critical angle of water in air?

[Answer: (a) from water to air; (b) 48.8o]

The speed of light is 2.5 x 108 m/s in transparent material A and 2.0 x 108 m/s in transparent material B.

For total internal reflection to occur, should the light be directed from (1) A to B or (2) B to A?

(b) What is the critical angle?

(a) B to A

(b) 53.1 degrees

A flint glass has a refractive index of 1.713 for red light, and 1.737 for blue light. A beam of white light is incident on a flat surface of the flit glass with an incident angle of 60o. What is the angle between the red light and blue light after refraction?

[Answer: 0.47o]

An object is located on the principle axis of a convex mirror. Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) virtual

b) upright

c) shrunk

d) other side

An object is located on the principle axis of a concave mirror. The object distance is larger than the curvature radius of the sphere. Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) real

b) inverted

c) shrunk

d) same side

An object is located on the principle axis of a concave mirror. The object distance is smaller than the curvature radius of the sphere but larger than the focal length. Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

c) magnified or shrunk

(d) on the same side or other side of the object?

a) real

b) inverted

c) magnified

d) same side

An object is located on the principle axis of a concave mirror. The object distance is smaller than the focal length. Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) virtual

b) upright

c) neither

d) same side

An object is 120 cm in front of a concave mirror that has radius or curvature 120cm.

(a) Calculate the image distance.

From your result, determine the following properties of the image:

(b) real or virtual

(c) upright or inverted

(d) magnified or shrunk

(e) on the same side or other side of the object?

[Answer: (a) 120 cm]

A virtual image of magnification +2.0 is produced when an object is placed 7.0 cm in front of a spherical mirror.

(a) Is the mirror (1) convex, (2) concave, or (3) flat?

(b) Find the radius of the curvature of the mirror.

[Answer: (a) concave (b) 28 cm]

A virtual image of magnification +0.5 is produced when an object is placed 5.0 cm in front of a spherical mirror.

(a) Is the mirror (1) convex, (2) concave, or (3) flat?

(b) Find the radius of the curvature of the mirror.

[Answer: (a) concave (b) 10 cm]

An object located on the principle axis of a converging lens. It’s outside of focal point but inside of the distance of 2f (f is the focal length). Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) real

b) inverted

c) magnified

d) other side

An object located on the principle axis of a converging lens and outside of the
distance of 2f (f is the focal length). Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) real

b) inverted

c) shrunk

d) other side

An object located on the principle axis of a converging lens and inside of focal point. Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b)upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) virtual

b) upright

c) magnified

d) same side

An object located on the principle axis of a diverging lens. Use ray diagram to determine the following properties of the image:

(a) real or virtual

(b) upright or inverted

(c) magnified or shrunk

(d) on the same side or other side of the object?

a) virtual

b) upright

c) shrunk

d) same side

A converging lens has a focal length of 20.0 cm.

(a) Find out the image distance for an object with object distance of 40.0 cm.

From your result, determine the following properties of the image:

(b) real or virtual

(c) upright or inverted

(d) magnified or shrunk

(e) on the same side or other side of the object?

a) 40 cm

b) real

c) inverted

d) neither, they are the same size

e) other side

An object is 10 cm from a lens. The resulting upright image is one-fifth as large as the object. What are the image distance and the focal length of the lens?

[Answer: q =2 cm, f = 2.5 cm]

An object is 8.0 cm from a lens. The resulting inverted image is one-fourth as large as the object. What are the image distance and the focal length of the lens?

[Answer: q = 2 cm, f = 1.6 cm]

To correct hyperopia (farsightedness), convex lenses are prescribed. If a senior citizen can read a newspaper only when he holds it no closer than 50 cm away, what focal length of lens should be prescribed so he can read when he holds the book 25 cm away?

[Answer: 50 cm]

To correct myopia (nearsightedness), concave lenses are prescribed. If a student can read her physics book only when she holds it no further than 18 cm away, what focal length of lens should be prescribed so she can read when she holds the book 35 cm away?

[Answer: -37 cm]

A metal sphere with radius 0.100 m and emissivity 0.9 is at a temperature of 400 oC. The ambient temperature is 100 oC. Calculate the total power radiated by the sphere, in Watts.

[Answer: 1191 W]

The radius of the Sun is 7.0 x 108 m and the surface temperature is 5800 K. Assume the sun radiates as a perfect black-body into vacuum space at 0 K. Calculate the total power radiated by the sphere, in Watts.

[Answer: 3.95 x 1026 W]

What is the de Broglie wavelength associated with a 1000-kg car moving at 25 m/s?

[Answer: 2.7 x 10^-38 m]

If the de Broglie wavelength associated with an electron is 7.5 x10-7 m, what is the electrons speed?
* Mass of electron is 9.1 x 10-31 kg

[Answer: 970 m/s]

Calculate the wavelengths for the first three spectral lines in Balmer series.

A hydrogen atom in its ground state (n = 1) is excited to the n = 5 level by absorbing photons. It then makes a transition to the n = 3 level and then from n = 3 level directly to the ground level.

(a) What is the wavelength of absorbed photon?

(b) What are the wavelengths of the emitted photons?

[Answer: (a) 95 nm, (b) 1282 nm and 103 nm]