Beam Photoelectric
2009
Photoelectric Effect Einstein Question?
According to Einstein, increasing the brightness of a beam of light without changing its color will increase:
a) the energy of each photon
b) the speed of the photons
c) the frequency of the photons
d) the number of photons
e) none of the above
Einstein’s equation governing the photoelectric effect is the following:
E = hν – φ
where h is Planck’s constant, ν is the frequency of light incident on a metal, and E is the energy of the emitted electrons. The constant φ is called the metal’s “work function,” and the following equation correlates it to a threshold frequency below which no light, regardless of its intensity, will eject photoelectrons:
φ = (h)(ν_crit)
where h is again Planck’s constant, and ν_crit is the critical frequency.
Scientists had observed that when light was shone onto a metal, it often caused electrons to be ejected. However, while classical theories predicted that as the intensity of light increased, so should the energy of the emitted electrons, this was not observed. Instead, the energy was proportional to the frequency of the incident light, and moreover, light of too low a frequency (below the metal’s work function divided by Planck’s constant) did not cause any electrons to be emitted, not even at tremendous intensity.
Einstein’s equation demonstrates that light is quantized, and that the photoelectric effect involves the absorption of a light quanta. Recalling that the energy of light is directly related to its frequency, he reasoned that only light above some threshold energy (frequency) was sufficient to dislodge electrons from the metal. Furthermore, increasing the intensity of the light has no effect on the energy of the ejected electrons; their energy depends only on the energy (frequency) of the incident light.
So to answer your question, increasing the brightness of a beam of light incident on a metal without changing its color (frequency or energy) will not have any effect on the speed, energy, or frequency of either the incident photons, or the electrons emitted. Instead, since light is quantized, a brighter light simply means more photons, which are capable of ejecting more electrons. Hence, the answer is (d).
Opening the photoelectric smoke detector
|
|
SECO-LARM E931CS22RRC ENTRY ALERT SYSTEM $61.98 The Seco-Larm Door Entry Chime is perfect for garage doors, overhead doors, or entry detection for store fronts. Other applications: offices, schools, warehouse, vehicle detection (driveway alert), etc. Optional second speaker available (E-931ACC-S)…. |
|
|
Enforcer E-931-S33PRQ Polarized Reflective Photoelectric Beam $61.51 The Enforcer E-931-S33PRQ allows you to protect and monitor indoor or outdoor spaces. Its polarized reflective beam sensor reduces the interference caused by shiny objects reflecting light back into the sensor, causing reliable monitoring and fewer false… |
|
|
Amico Through Beam PNP NO DC Infrared Ray Photoelectric Switch $17.04 An opposed (through beam) arrangement consists of a receiver located within the line-of-sight of the transmitter. In this mode, an object is detected when the light beam is blocked from getting to the receiver from the transmitter. Can be applied in security system, manufacturing industry…. |
|
|
Enforcer Indoor/Outdoor Wall Mounted Photoelectric Beam Sensor with 35 Foot Range $38.99 Increase security to exterior entryways of your home or office by installing the Enforcer Indoor/Outdoor Wall Mounted Photoelectric Beam Sensor. The Transmitter/Receiver sensor has a rugged all-weather waterproof enclosure and a range of up to 35 feet tha… |
|
|
Enforcer E-931CS22RRCQ Retro-Reflective Photoelectric Sensor Entry Alert System $59.92 The Enforcer E-931CS22RRCQ is an easy, reliable way to monitor doors and entrances in your home or business. This is a standalone system, including a sensor, reflector, adapter, and chime unit, meaning you can set it up in a variety of areas. The speaker… |
|
|
Single Beam Photoelectric Detector Infrared Sensor 1 Pair $13.97 Size (Each One): 7.5 x 4.8 x 3cm/3” x 1.9” x 1.2” (L*W*T); Operating Temperature: -20°C to 70°C; Shape (Each One): Half Egg Shaped; Package Content: 1 Pair x Active Infrared Detector 1 x English Usage Manual 1 Bag x Install Tools; This is Active Infrared Detector. Install each pair at the opposite positions. Then there is a infrared area between these two detector parts. When someone passes… |
|
|
Omron E3JM Garage Door Opener Photoelectric Sensor Photoelectric Sensor with Built-in Power Supply and Wiring Terminal Block for Easy Maintenance and Reliable Operation. Available for both AC and DC, with self-contained timer function. Easy-to-wire with stepped terminal block system. Provides polarized beam for reliable detection of shiny object (Retro-reflective Models). Relay output and transistor output models (contact output: SPDT). … |
|
|
Optex AX-100TFR 100 Foot Outdoor Photoelectric Detector $419.30 The Optex AX-100TFR 100 Foot Outdoor Photoelectric Detector is a revolution in the perimeter security industry, offering a significant cost saving alternative to a traditional hardwired system. No trenching is required, drastically reducing installation c… |
|
|
Dual Beam Infrared Photoelectric Beam Detector with Intelligent Voice Alarm This is Dual Beam Infrared Photoelectric Beam Detector with Intelligent Voice Alarm. It has integrated design, installation brackets, the most convenient installation. It can offer holographic spot real-time report, by nique displacing receiving, transmitting parts with big power. It also can provide full function checking, self-adaption in environment and trouble locking and patented balanced che… |
|
|
Investigation of the H/P 5062 series cesium beam resonator electron multiplier decay problem … |
Comment