AnswersDriveA photoresistor (or light-dependent resistor, LDR, or photo-conductive cell) is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.
Correspondingly, what is LDR how it works?
An LDR is a component that has a (variable) resistance that changes with the light intensity that falls upon it. This allows them to be used in light sensing circuits.
How can test LDR?
Keep the multimeter at Ohms mode. The LDR must be subjected to darkness by covering it with an opaque paper. Connect the LDR leads to the multimeter terminals as shown in the figure. Now the multimeter will show a high resistance reading around 200K.
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What is the basic function of a transistor?
It can amplify and switch electrical power and electronic signals. Transistors are made of semiconductor material with three or more terminals used to connect to an external circuit. By applying a current or a voltage to one of the pairs of the terminals, there is a change in current through another pair of terminals.
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What is a Photoresistor made out of?
Modern light dependent resistors are made of lead sulfide, lead selenide, indium antimonide, and most commonly cadmium sulfide and cadmium selenide. The popular cadmium sulfide types are often indicated as CdS photoresistors.
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What is photocell in physics?
A photocell is a practical application of the phenomenon of photoelectric cell. CONSTRUCTION. A photocell consists of an evacuated sealed glass tube containing a wire anode and a concave cathode of suitable emitting material such as Cesium (Cs) The material of cathode responds to a given frequency range.
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What does a photocell do on a light?
Photocells a.k.a CdS cells, photoresistors, LDR (light dependent resistor) Photocells are sensors that allow you to detect light. They are small, inexpensive, low-power, easy to use and don't wear out. For that reason they often appear in toys, gadgets and appliances.
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What are the effects of photoelectric?
The photoelectric effect is the emission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner can be called photo electrons. This phenomenon is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry or electrochemistry.
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How do we know light acts like a wave?
Light behaves as a wave - it undergoes reflection, refraction, and diffraction just like any wave would. Yet there is still more reason to believe in the wavelike nature of light. Continue with Lesson 1 to learn about more behaviors that could never be explained by a strictly particle-view of light.
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How can light be a particle?
Now that the dual nature of light as "both a particle and a wave" has been proved, its essential theory was further evolved from electromagnetics into quantum mechanics. Einstein believed light is a particle (photon) and the flow of photons is a wave.
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Is light a photon?
Einstein called these energy packets photons, and these are now recognised as a fundamental particle. Visible light is carried by photons, and so are all the other kinds of electromagnetic radiation like X-rays, microwaves and radio waves. In other words, light is a particle.
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Why is light like a particle?
Quantum mechanics tells us that light can behave simultaneously as a particle or a wave. When UV light hits a metal surface, it causes an emission of electrons. Albert Einstein explained this "photoelectric" effect by proposing that light – thought to only be a wave – is also a stream of particles.
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How fast is light?
The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second), and in theory nothing can travel faster than light. In miles per hour, light speed is, well, a lot: about 670,616,629 mph. If you could travel at the speed of light, you could go around the Earth 7.5 times in one second.
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Is a photon a wave or a particle?
The photon has zero rest mass and always moves at the speed of light within a vacuum. Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles.
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Is a photon matter?
If by "matter" you mean massive (in the sense of having nonzero rest mass), then photons are not matter. Photon is a fundamental particle, a force carrier for electromagnetic interaction. It has zero charge, zero rest mass, and is a spin 1 particle (a boson).
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Can you see a photon?
First of all, yes, the rods and cones in the retina are sensitive to single photons. However, such tiny signals are filtered out during the image processing in the optic nerve and brain. It takes 7-30 photons to "see" an event, so no you would not see a single photon. (Please enjoy a picture of a human eye.)
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How a photon is created?
A photon is produced whenever an electron in a higher-than-normal orbit falls back to its normal orbit. During the fall from high energy to normal energy, the electron emits a photon -- a packet of energy -- with very specific characteristics.
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Can a photon be destroyed?
Photons are not indestructible. They can be destroyed, as they undergo 'absorption' when traveling through matter. A photon is basically, a quantum of electromagnetic energy. In the process of absorption, one or more photons can be absorbed by nuclear particles or atoms, and basically get destroyed.
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What happens to an electron when it releases a photon?
When an electron absorbs energy, it jumps to a higher orbital. An electron in an excited state can release energy and 'fall' to a lower state. When it does, the electron releases a photon of electromagnetic energy. The electron can absorb one quantum of energy and jump up to the excitation state.
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How the light is produced?
As the electrons change orbital levels, energy is emitted or absorbed. For example, if we burn a sheet of paper, energy is given off, which we see as a flame. The matter in the filament of a light bulb emits light when it is excited by an electrical current.
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What happens when an atom emits a photon of light?
Contrary to the present-day belief, which suggest that, an atom emits a photon of light when an electron jumps from a high-energy level to a low-energy level (i.e. from an outer orbital to an inner orbital), the electrons in a non-excited atom are motionless, and an atom emits photons because of the vibration of the