Question

Discuss how the colors of the filters and their spectrums relate. When two filters are placed in series, what is the resulting % transmittance? How does one make a bandpass filter?

Explain the relationship between absorbance and concentration and also the % transmittance and concentration.

Answer 1

relationship between absorbance andconcentration can be deduced from beer lambert law that is

absorbance= molar extinction coefficient* concentration* optical path length= E*C*L...... (1)

so absorbance is directly proportionl to concentration.

since absorbance is always given as ; A= 2- log(%T) where T is transmittance

so from (1)

E*C*L= 2-log%T

C= 2-log%T / E*L

Now for answering how to make bandpass filter? answer is :

a Band Pass Filters passes signals within a certain “band” or “spread” of frequencies without distorting the input signal or introducing extra noise.

complete schematics of bandpass filter

now for the relation between colour of filter and spectrum:

Filters do not change the light's frequency as it passes through the medium. It literally filters out the bands of light it is designed to block. first think about colours of light. The three primary colours are red, green and blue. Red and green make yellow, green and blue make cyan, red and blue make magenta. All three together make white.

Now, a blue filter only let's blue light through. If you shine blue light on it, blue light comes out the other side. If you shine white light on it, the red and green are blocked and the blue goes through.
So, magenta light on a blue filter will result in blue light going through as magenta contains blue. However, red light hitting a blue filter will all be blocked. No light will go through.

now since tranmittance is multiplicative in nature. so if you place 2 filters in series the overall transmittance will be T₁*T₂