How to Measure Light Flashcards
What is a Transducer?
A transducer is a device that converts one form of energy into another.
PMT and CCD are types of transducers that convert light into electrical signals.
transducers use P-type and N-type semiconductors to achieve efficient conversion of signals (e.g., photodiodes)
What is a Photomultiplier Tube?
PMT
This is a type of transducer
highly sensitive device used to detect and amplify very low levels of light.
using the photoelectric effect photons strike a photocathode, releasing electrons. These electrons are then multiplied through a series of dynodes, resulting in a large electrical signal.
The main concept of the Photomultiplier Tube is that small amounts of photons can create a large signal.
T or F
T
What is a Charge Couple Device?
CCD
This is a type of transducer.
image sensor that converts light into electrical signals.
consists of an array of P-type and N-type semiconductors that act like buckets to store electrons from photons.
It can amplify the signal and transfer electrical charge by changing voltage.
What are P-type and N-type Semiconductors?
types of semiconductors used in electronic devices.
When combined (as in a PN junction), they form diodes, transistors, and other semiconductor devices that control electrical current
What is a P-type semiconductor?
Is it positively or negatively charged?
e.g Aluminium
Has 3 valence electrons in an area where other elements have 4 valence electrons.
This lack of an electron gives it a positive charge.
What is a N-type semiconductor?
Is it positively or negatively charged?
e.g Silicon
Has 5 valence electrons in an area where other elements have 4 valence electrons.
This extra electron gives it a negative charge.
What happens with you join P and N type semiconductors?
This is called Doping of a semiconductor.
Due to their positive and negative charges they attract and share electrons.
This occurs spontaneously to form a depleted region with no charge.
What is a diode?
two-terminal semiconductor device that allows current to flow in only one direction.
The key component of a diode is a PN junction, which is formed by joining a P-type and an N-type semiconductor.
What is electricity?
The continuous movement of electrons through a conductor
Flow of charge/ current.
Describe the two methods of generating electricity from semiconductors.
The first method
- Adding positive/negative charge to depleted region can speed up the flow of charges from the positive and negative reservoirs.
If you add positive charge to the positive reservoir it will flow to the negative side.
Describe the two methods of generating electricity from semiconductors.
The second method
Light emitting Diode
- Add positive/negative charge to the reservoirs to induce the depleted region.
Add positive charge to the positive reservoir (P type)
and vice versa for the N type.
This emits light and is how leds work.
Infrared Spectrometry is next to red on the EM spectrum.
T/F
T
Longer wavelength =
lower energy
T/F
T
Why do we look at Infrared Spectrometry to identify compounds.
Many bonds between molecules vibrate at Infrared frequencies.
So if you pass infrared through a sample you can look for characteristic resonance emission / absorption
In Infrared Spectrometry what is the relationship between Bond strength and frequency?
and how does this relate with vibration?
Strength of bond determined frequency
weak bond strength= low frequency . it also vibrates slowly.
Between single, double and triple bonds in Two Nitrogen atoms, which has the highest frequency.
The triple bond because it it the strongest bond.
How do you identify a compound on IR Spectrum?
Every functional group has a characteristic range on the IR Spectrum
What type of band does OH group in water and alcohol have on IR spectrum?
broad band
What is the fingerprint region?
The fingerprint region refers to the unique part of an infrared (IR) spectrum found in the wavenumber range of 400 cm⁻¹ to 1500 cm⁻¹.
This region contains complex absorption patterns due to various vibrational modes of a molecule, making it highly specific for identifying compounds—just like a human fingerprint.
How to read IR spectrum ?
a peak is actually a dip in the spectrum. This means that the signal is absorbed.
