Electricity
An electrical device uses 5 A when connected to a 100 V power source. What is the resistance of the device?
R = V/I = 100 V / 5 A = 20 ohms
What type of materials are permanent magnets made from?
Permanent magnets are formed from a class of materials known as ferromagnetic
Rank the Speed of Light from largest to smallest in: (a) Crystal with index of refraction 1.81 (b) Redbull with index of refraction 1.33 (c) Jade with index of refraction 2.25
b>a>c
Describe the characteristics of the image formed by a plane mirror. Upright or inverted, enlarged or smaller or same, real or virtual?
A plane mirror produces a virtual image that is upright, the same size as the object, and located the same distance behind the mirror as the object is in front of the mirror.
What is the photoelectric effect?
In the photoelectric effect, when a metal surface is exposed to light, electrons are emitted from the metal. The wavelength of the light must be less than a critical value that varies from metal to metal.
What is the difference between series and parallel connections of elements in a circuit, e.g., light bulbs?
Devices connected in series have slower currents passing through them. Devices connected in parallel have faster currents passing through them.
What are the two types of magnets?
The two types of magnets are permanent magnets and electromagnets (currents in wires).
How is a ray of light bent when it goes from air into glass? How is a ray of light bent when it goes from water into air?
(a) A ray propagating from air into glass is bent toward the normal. (b) A ray going from water into air is bent away from the normal. The normal is the imaginary line that is perpendicular to the boundary surface.
What type of mirror is used to produce a magnified image of an object?
Concave
What is a photon?
A photon is a quantized packet of energy
What is direct current or DC? What uses it?
With direct current or DC, the current always flows in one direction. Direct current is produced by batteries.
What is the effect of a magnetic field on a charged particle?
A magnetic field produces a deflection on a moving charged particle. Charged particles revolve around magnetic field lines in spiral orbits
What is the phenomenon of refraction and how is it characterized by the index of refraction?
Refraction is the bending of a light ray as it enters the boundary between two materials. The amount of bending depends on the indices of refraction of the two media.
What is a real image and a virtual image?
In a real image, light rays actually converge at the image location. In a virtual image, light rays diverge when they leave the object and appear to come from a point where no light rays actually are.
What is fluorescence?
Fluorescence is a process whereby a substance absorbs a high energy photon and immediately emits a lower energy photon. For example, ultraviolet light (black light) is absorbed by a fluorescent material which then emits green light.
What are the advantages of AC vs. DC power?
Voltages in an AC power system can be changed using transformers, and AC plants can be located far away from the cities they supply.
The green laser pointer used in class has a frequency of 5.645 x 10^14 Hz. What is the wavelength?
3x10^8 / 5.64 x 10^14 = 5.32 x 10^7 m = 532 nm.
What phenomenon is the cause of blue skies and red sunsets?
Blue skies and red sunsets are the result of the scattering of sunlight from air molecules. The scattering depends strongly on wavelength.
What type of image is formed of an object located far from a converging lens?
For an object located well beyond the focal point of a converging lens, the image is real, and inverted.
Two photons have frequencies f1 = 1.0 x 10^14 Hz, and f2 = 1.0 x 10^15 Hz. What is the ratio E2 /E1 of the energies of these two photons?
E = hf, so photon 2 has 10 times more energy than photon 1 so E2 /E1 = 10.
How is AC power produced?
AC power is produced in an electrical generator which consists of a coil of wire that is rotated in a magnetic field.
What is an electromagnetic wave?
An electromagnetic wave is a particular combination of timeâvarying electric and magnetic fields that propagate through space at the speed of light.
What is total internal reflection?
Total internal reflection is an optical phenomenon that occurs when a light ray starting in a medium of index of refraction n1 is reflected at the boundary of another medium with index of refraction n2 < n1. This only occurs if the angle of incidence is greater than some critical value that depends on the materials.
How can a converging lens be used as a magnifying lens?
A converging lens can be used to produce an enlarged image if the object is placed within the focal length of the lens.
What is the difference between emission and absorption?