Light And Sound Flashcards
Sound is a wave whose speed cannot be changed by intensity but?
The medium it is traveling in i.e. air
For sound what are the two relative characteristics of medium?
- Bulk Modulus: measure of the medium’s resistance to compression
higher bulk modulus (more the medium resists) → faster sound waves travel
- Density: With more mass/vol or higher density there is more resistance to motion and lower speeds of sound
Sound of speed is faster from highest to lowest
Solid then liquid then gas
Solids have the highest bulk since they’re fully compressed while gas has the lowest bulk
Lower density within gases means what speed of sound?
Higher i.e. speed of sound increases as the density decreases (because higher density resists the motion)
What’s the equation for speed of sound?
V = Sq. root (Bulk/density)
What’s true for all waves?
As waves change medium, the speed will increase or decrease and change wavelengths larger or smaller respectively but frequency will stay same
Humans can hear sounds with frequency from 20-20,000 Hz. What are the other sounds called?
Under 20 Hz infrasonic and above 20,000 Hz it is ultrasonic
What does frequency depend on?
- Wave velocity: the faster the wave is moving the higher the frequency will be
- Wavelength: distance from compression to compression, the larger the wavelength the lower frequency will be
What’s equation for frequency and wave speed?
V (wave speed) = frequency * wavelength
What’s the equation for Doppler effect?
f’ = f (v +- vD)/(v+- vS)
f’ = perceived frequency
f = actual emitted frequency
v= speed of sound in medium
vD = speed of detector
vS = speed of source
In the eq, if detector moves towards the source, we add and if away we subtract
Meanwhile, if source moves towards the detector, we subtract and if away we add
What’s refraction in light waves?
It occurs when light moves from one medium to another
What are photons?
Energy through which light travels
What does light occur as?
It can occur as a wave or a particle depending on the situation
What’s dispersion?
Spreading of light due to differences in the indices of refraction of different colors
What’s the point called where lights meet?
Focal point
What’s a convex lens?
A lens which has both sides bulging outward. It bend incoming light towards the focal point
What’s real image?
It’s inverted produced by a single lens
What’s diverging of light?
When light rays spread apart instead of coming to a point
What’s concave lens focal point?
It’s where the light is originated from and then gets apart. Notice the focal point doesn’t have all light rays passing through it i.e. that’s why it is called a diverging lens
What are virtual images like?
Always upright and not flipped, and they always make the objects in the mirror seem smaller
What do concave lens and convex mirror do?
Diverging and always produce virtual image
What do convex lens and concave mirror do?
Converging:
Image is real when object distance > focal length
Image is virtual when object distance < focal length
What happens in converging system?
The closer the object is the bigger the image
F: Image is closer i.e. larger
2F: image is same size as object
SIR: image is minimized as it’s far.
Note at all points image is real and inverted
What are focal length and power for diverging systems?
Negative
What’s the equation for power of lens or mirror?
Power = 1/f = 1/image distance + 1/obj. distance
At converging system if object is even closer than focal point then it’s BUV?
Image is Bigger, upright, and virtual
What’s the mnemonic for diverging system (concave lens and convex mirror)
SUV: Image is smaller, upright, and Virtual
What are the important factors for IR spectrum?
Leftmost part from 4000 to 2500 corresponds to bonds containing H atoms. Most useful bonds are OH bond (broad peak) or NH bond (sharp peak) around 3300 cm-1
Note: If N has two hydrogens attached then there will be two peaks
Middle of spectrum from 2500 to 1000 cm-1 contains bonds without Hydrogens such as double or triple bonds (that have higher frequency than single bonds)
Most imp. double bond is C-O or Carbonyl which creates strong, sharp peak at 1700 cm-1
Below 1000, is fingerprint region
How does NMR works?
Each peak in proton NMR corresponds to different type of proton. Chemically same protons give a same peak. So two peaks mean two types of protons
What does it mean when one peak is larger or one is shorter?
larger peak is made of multiple similar protons while smaller peak is usually representing just one lone proton
Things to remember for NMR spectra?
Aldehyde protons peak between 8-10 ppm
Carboxylic Acid proton peak between 10-12 ppm
Aromatic proton peak between 6-8 ppm
Splitting in peaks is caused due to?
Due to adjacent protons
