Course Revision Questions Physics Ch.1
What is the second law of refraction?
The ratio of the sine of the angle of incidence to that of the angle of refraction is a constant.
What is the maximum value the angle of refraction can have which corresponds to an angle of incidence called the "critical angle"? (measure the value to the nearest degree).
90
Briefly describe the parallel beam?
A collection of parallel rays propagating in the same direction.
Briefly describe the divergent beam?
A collection of rays that emanate (or appear to come out) from one point.
Briefly describe the convergent beam?
A collection of rays that meet (or appear to do so) at one point.
What are the essential components of a simple camera?
A lens, an aperture, a focusing ring, a shutter and film.
What are the properties of the image given by the prism binoculars?
A magnified erect image.
What is the equipment needed to determine the position of the image of a pin in a plane mirror?
A plane mirror with a straight edge that can be stood vertically, a white sheet of paper, a cardboard or soft board flat horizontal surface, 5 pins, a sharp pencil, and a ruler.
Which object reflects more light, a grey or a white one? If an object neither emits nor reflects light, what would it look like? Give an example of such an object.
A white object would reflect more. It would be transparent like glass.
Define virtual image.
An image formed at the imaginary intersection of light rays emerging from an optical system.
Define real image.
An image formed at the real intersection of light rays emerging from an optical system.
When walking or riding a car, objects in the close scenery seem to move faster than the far ones. Explain this observation.
As we move, our relative distances to objects in the close scenery and the far ones changes.
How can a virtual image be seen?
Can be detected by an observer who places his eyes in the path of the beam, anywhere beyond the lens.
Give some examples of light sources and identify the origin of their energy. Classify these sources into natural and artificial.
Candle light: chemical energy, artificial source. Lightning bolts: electrostatic energy, natural source
The Sun, to a terrestrial observer, appears to be a 32′ wide luminous disk. Its distance from the Earth is L = 1.50 × 10^8km. Find the diameter D of the Sun. (Answer is explained through the course revision answer sheet.)
D= 1.39x10^6km
How is your brain capable of computing a qualitative impression of distance?
Each eye is turned by a different angle when looking at the same object. The brain "measures" this angle and determines how far it is from the observer.
What are the properties of the image given by the astronomical refracting telescope?
First lens gives a real inverted image and the second lens gives a virtual, magnified and inverted image.
When do we see a beam of light?
In a dusty or foggy area in which light illuminates dust particles or water droplets.
Enumerate the properties of the image of an extended real object in a plane mirror.
It is a virtual image; the image has the same size as the object the image is laterally inverted but vertically erect.
What happens to light energy when a beam of direct sunlight is passed through a magnifying glass? Does the glass get heated? Is energy conserved?
Light energy is concentrated, the glass gets heated, and energy is conserved.
Explain how a book used in the example is illuminated; does light fall directly on the book from the source or after reflections off different surfaces? Identify the source(s) of light. Is light reflected from black or white regions on the page? How can you tell?
Light falls directly from source on book. The light bulb is the source of light. Light is reflected off the white regions of the page.
Why can't we see around obstacles?
Light only propagates in straight lines and doesn't bend around obstacles nor does it go through them.
Suggest a way to measure the focal length of a converging lens.
Move the lens until a sharp image of the object is formed alongside the object. The image will be sharpest when it is exactly the same size as the object. Measure the distance between the optical center of the lens and the grid object. This distance is the focal length of the converging lens. Repeat many times and find the average focal length of the lens.
List the three types of beams.
Parallel beam, divergent beam, and convergent beam.
Give other examples supporting the fact that light is a form of energy.
Solar panels
Define the angle of incidence.
The angle that the incident ray makes with the normal at the point of incidence.
Define the angle of reflection.
The angle that the reflected ray makes with the normal at the point of incidence.
An electric bulb (B), treated as a point source emitting light in all directions, is put inside an opaque, matte (dull), black cylinder as shown in the figure. The cylinder in suspended vertically from the ceiling above a horizontal table. Using the principle of rectilinear propagation of light, determine graphically the illuminated region on the table, and identify its shape.
The illuminated region in the table is where light falls from the point source directly. The shape of the illuminated region is circular.
What are the characteristics of the image formed by a converging lens for f< p< 2f?
The image is real, inverted, magnified at d > 2f.
What are the characteristics of the image formed by a converging lens for 0 < p< f?
The image is virtual, erect and magnified.
What is the first law of reflection?
The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane called the plane of incidence.
What is the first law of refraction?
The incident ray, the refracted ray, and the normal at the point of incidence all lie in the same plane called plane of incidence.
Give examples of illumination by reflected light.
The moon.
What does the point of incidence represent?
The point at which the incident ray meets the boundary.
If the angle of incidence is 0º what would the angle of reflection be?
The ray of light strikes the surface normally which would cause it to reflect back on itself with an angle of reflection = 0.
Give some examples of diffuse reflection. In cinema theaters, screens reflect light from the projector into the spectators' eyes. Is this specular or diffuse reflection?
The reflection has to be diffuse for every person in the audience to be able to watch the movie.
What does the pin method help us conclude?
We conclude that the angles of incidence and reflection are equal and they, along with the normal, lie within the same plane.
When do we see an object?
When light reflects from the object to reach our eyes.
A passenger, looking in the rear view mirror of a cab, sees the eyes of the driver. Does the driver see the passenger's eyes when he looks in the mirror?
Yes, because of the reversibility of light.
The index of refraction of diamond is 2.42 and that of water is 1.33. a)Specify which of these two media is more refractive. Justify. b)Find the velocity of light in each of these media.
a)Diamond b)vdiamond= 1.24x10^8m/s vwater=2.26x10^8m/s
Describe the behavior of a light beam as it crosses the interface of two media, where the first medium has an index of refraction n1 and the second medium has an index of refraction n2 such that: a)n1<n2 b)n1>n2
a)The ray of light is leaving one medium to an optically denser medium. It will deviate towards the normal. b)The ray of light is leaving one medium to an optically less dense medium. It will deviate away from the normal.
Magnification properties. Look at a printed word though the lens. How does it look through: a) a converging lens? b) a diverging lens?
a)magnified b)diminished
What is the shape of: a) a converging lens? b) a diverging lens?
a)thin-edged lens b)thick-edged lens
What would be the angular size of the Sun with respect to an observer on Pluto, whose average distance from the Sun is 39.5 times that of Earth? (Answer is explained through the course revision answer sheet.)
a=0.806'
State the value of the speed of light, c, and the factors that determine the amount of refraction a beam of light undergoes when passing from one medium to another.
c = 3x10^8m/s. The change in index of refraction between the media. The angle of incidence (angle between light beam and normal to surface).
A magnifying glass is nothing but a ___________ lens.
converging
The correct order for setting up an experimental study of converging lenses is a light bulb followed by a _______________ then a _______ to collect the image produced on.
converging lens, screen
A1.50 m boy, standing 2.0 m from the edge of a 3.0 m deep empty swimming pool, cannot see a coin at the bottom. He can see the coin only when the pool is completely filled with water. How far is the coin from the wall of the swimming pool?
d = 2.25 m
Experimental studies of converging lenses are usually performed to study the behavior of the ______ produced.
image
Calculate the index of refraction of a substance in which the speed of light is 2.25x10^8m/s.
n = 1.33
A ray of light passing through water, strikes the plane face separating water from air at an angle of incidence of 30°. Find the angle of refraction.
r = 40.6
A ray of passing through air strikes the plane face of a water vessel (n = 1.33) at an angle of incidence of 60o. Find the angle of refraction.
r=40.6
