1. If the concentration of the solution is more than 10^-2M (0.01M) in that case the linear relation is not obtained, when we plot a graph of Absorbance V/s concentration. That means law is deviated.

2. The molar extinction coefficient ε depends on the refractive index of absorbing medium. If the initial concentration of the absorbing medium is greater than 10^-2 M then refractive index changes and so ε changes. If the concentration is less than 0.01M the refractive index does not change with the concentration and so the ε does not changes and law holds true.

3. The low also fail, if the absorbing spices react with the solvent i.e. either association or dissociation takes place. $$ \underset { Orange }{ { Cr }_{ 2 }{ O }_{ 7 }^{ -2 } } + { H }_{ 2 }O \Longrightarrow 2{ H }^{ + } + 2\underset { Yellow }{ { CrO }_{ 4 }^{ -2 } }$$

4. The law is also deviated if the monochromatic light is not used.

5. Change of temperature also leads to deviation of Beer-Lamberts Law.

6. The deviation may occur if the width of the instrument is not proper.

7. The deviation also occurs in the instrument where filters are used because with filters we do not get monochromatic light.

1. If the concentration of the solution is more than 10^-2M (0.01M) in that case the linear relation is not obtained, when we plot a graph of Absorbance V/s concentration. That means law is deviated.

2. The molar extinction coefficient ε depends on the refractive index of absorbing medium. If the initial concentration of the absorbing medium is greater than 10^-2 M then refractive index changes and so ε changes. If the concentration is less than 0.01M the refractive index does not change with the concentration and so the ε does not changes and law holds true.

3. The low also fail, if the absorbing spices react with the solvent i.e. either association or dissociation takes place. $$ \underset { Orange }{ { Cr }_{ 2 }{ O }_{ 7 }^{ -2 } } + { H }_{ 2 }O \Longrightarrow 2{ H }^{ + } + 2\underset { Yellow }{ { CrO }_{ 4 }^{ -2 } }$$

4. The law is also deviated if the monochromatic light is not used.

5. Change of temperature also leads to deviation of Beer-Lamberts Law.

6. The deviation may occur if the width of the instrument is not proper.

7. The deviation also occurs in the instrument where filters are used because with filters we do not get monochromatic light.

Beer-Lambert's Law states that “Equal fractions of incident light are absorbed by successive layers of equal thickness and equal concentration of absorbing medium.” We know that Lambert's Law is $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l $$ And Beer's Law is $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K''c $$ On combining both, we get Beer-Lambert's Law which is, $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l K''c $$ $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = Kcl $$ $$ \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = \frac { K }{ 2.303 } cl $$ $$ \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = \varepsilon cl $$ where \(\epsilon\) is constant and \(\epsilon = \frac { K }{ 2.303 }\) is known as molar extinction coefficient Or molar absorptivity and it is defined as “the reciprocal of the thickness which produces transmitted ray \(\frac { 1 }{ 10 }\) of its incident rays if the concentration of the absorbing species in the solution is 1mole.”

The unit is \({ dm }^{ 3 } { mole }^{ -1 } { m }^{ -1 }\).

But Optical density is defined as logarithm of ratio of \({ I }_{ 0 }\) to \({ I }_{ t }\). Therefore, $$ \boxed { \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = Optical \ density \ (O.D.) = \ Absorbance \ (A) } $$ OD has no unit and its value lies between 0 to 1. Also Transmittance T is defined as the fraction of the light transmitted. $$ T = \frac { { I }_{ t } }{ { I }_{ 0 } } $$ The value of T is always small to convert in to appreciable it is always expressed in percentage.

Thus Beer-Lambert's Law becomes, $$ \boxed { O.D = A = \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = -\log { T } = \varepsilon cl } $$

Beer-Lambert's Law states that “Equal fractions of incident light are absorbed by successive layers of equal thickness and equal concentration of absorbing medium.” We know that Lambert's Law is $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l $$ And Beer's Law is $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K''c $$ On combining both, we get Beer-Lambert's Law which is, $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l K''c $$ $$ 2.303\log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = Kcl $$ $$ \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = \frac { K }{ 2.303 } cl $$ $$ \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = \varepsilon cl $$ where \(\epsilon\) is constant and \(\epsilon = \frac { K }{ 2.303 }\) is known as molar extinction coefficient Or molar absorptivity and it is defined as “the reciprocal of the thickness which produces transmitted ray \(\frac { 1 }{ 10 }\) of its incident rays if the concentration of the absorbing species in the solution is 1mole.”

The unit is \({ dm }^{ 3 } { mole }^{ -1 } { m }^{ -1 }\).

But Optical density is defined as logarithm of ratio of \({ I }_{ 0 }\) to \({ I }_{ t }\). Therefore, $$ \boxed { \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = Optical \ density \ (O.D.) = \ Absorbance \ (A) } $$ OD has no unit and its value lies between 0 to 1. Also Transmittance T is defined as the fraction of the light transmitted. $$ T = \frac { { I }_{ t } }{ { I }_{ 0 } } $$ The value of T is always small to convert in to appreciable it is always expressed in percentage.

Thus Beer-Lambert's Law becomes, $$ \boxed { O.D = A = \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = -\log { T } = \varepsilon cl } $$

In 1852 Beer has given the statement which is known as Beers Law. It states that “Equal fraction of Incident Light is absorbed by equal concentration of absorbing medium.” Or “When monochromatic light is incident on a medium the rate of decrease of intensity of light with concentration of the medium is proportional to the intensity of light incident on it.”

If \({ d }_{ i }\) is the decrease in intensity of light or absorbed intensity of light by the thickness \({ d }_{ c }\) and \(I\) is the intensity of light incident on it, then, $$- \frac { { d }_{ i } }{ { d }_{ c } } \propto I $$ The negative sign is for decrease in intensity of incident light. $$ - \frac { { d }_{ i } }{ { d }_{ c } } = K''I $$ OR $$ - \frac { { d }_{ i } }{ I } = K''{ d }_{ c } $$ On integrating the equation between limits when \(c = 0\) then \(I = { I }_{ 0 }\) and when \(c = c\) then \(I = { I }_{ t } \) $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = \int _{ 0 }^{ c }{ K''{ d }_{ c } } $$ $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = K''\int _{ 0 }^{ c }{ { d }_{ c } } $$ $$ - \ln { \frac { { I }_{ t } }{ { I }_{ 0 } } } = K''c $$ $$ \ln { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K''c $$ $$ \boxed { 2.303 \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K''c } $$ Where \({ I }_{ 0 }\) is the intensity of incident radiation and \({ I }_{ t }\) is intensity of transmitted radiation. Equation is known as Beers Absorption Equation.

In 1852 Beer has given the statement which is known as Beers Law. It states that “Equal fraction of Incident Light is absorbed by equal concentration of absorbing medium.” Or “When monochromatic light is incident on a medium the rate of decrease of intensity of light with concentration of the medium is proportional to the intensity of light incident on it.”

If \({ d }_{ i }\) is the decrease in intensity of light or absorbed intensity of light by the thickness \({ d }_{ c }\) and \(I\) is the intensity of light incident on it, then, $$- \frac { { d }_{ i } }{ { d }_{ c } } \propto I $$ The negative sign is for decrease in intensity of incident light. $$ - \frac { { d }_{ i } }{ { d }_{ c } } = K''I $$ OR $$ - \frac { { d }_{ i } }{ I } = K''{ d }_{ c } $$ On integrating the equation between limits when \(c = 0\) then \(I = { I }_{ 0 }\) and when \(c = c\) then \(I = { I }_{ t } \) $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = \int _{ 0 }^{ c }{ K''{ d }_{ c } } $$ $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = K''\int _{ 0 }^{ c }{ { d }_{ c } } $$ $$ - \ln { \frac { { I }_{ t } }{ { I }_{ 0 } } } = K''c $$ $$ \ln { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K''c $$ $$ \boxed { 2.303 \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K''c } $$ Where \({ I }_{ 0 }\) is the intensity of incident radiation and \({ I }_{ t }\) is intensity of transmitted radiation. Equation is known as Beers Absorption Equation.

In 1760 Lambert has given the statement which is known as Lamberts Law. It states that “Equal fraction of Incident Light is absorbed by equal thickness of absorbing medium.” Or “When monochromatic light is incident on a medium the rate of decrease of intensity of light with thickness of the medium is proportional to the intensity of light incident on it.”

If \({ d }_{ i }\) is the decrease in intensity of light or absorbed intensity of light by the thickness \({ d }_{ l }\) and \(I\) is the intensity of light incident on it, then, $$- \frac { { d }_{ i } }{ { d }_{ l } } \propto I $$ The negative sign is for decrease in intensity of incident light. $$ - \frac { { d }_{ i } }{ { d }_{ l } } = K'I $$ OR $$ - \frac { { d }_{ i } }{ I } = K'{ d }_{ l } $$ On integrating the equation between limits when \(l = 0\) then \(I = { I }_{ 0 }\) and when \(l = l\) then \(I = { I }_{ t } \) $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = \int _{ 0 }^{ l }{ K'{ d }_{ l } } $$ $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = K'\int _{ 0 }^{ l }{ { d }_{ l } } $$ $$ - \ln { \frac { { I }_{ t } }{ { I }_{ 0 } } } = K'l $$ $$ \ln { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l $$ $$ \boxed { 2.303 \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l } $$ Where \({ I }_{ o }\) is the intensity of incident radiation and \({ I }_{ t }\) is intensity of transmitted radiation. Equation is known as Lamberts Absorption Equation.

In 1760 Lambert has given the statement which is known as Lamberts Law. It states that “Equal fraction of Incident Light is absorbed by equal thickness of absorbing medium.” Or “When monochromatic light is incident on a medium the rate of decrease of intensity of light with thickness of the medium is proportional to the intensity of light incident on it.”

If \({ d }_{ i }\) is the decrease in intensity of light or absorbed intensity of light by the thickness \({ d }_{ l }\) and \(I\) is the intensity of light incident on it, then, $$- \frac { { d }_{ i } }{ { d }_{ l } } \propto I $$ The negative sign is for decrease in intensity of incident light. $$ - \frac { { d }_{ i } }{ { d }_{ l } } = K'I $$ OR $$ - \frac { { d }_{ i } }{ I } = K'{ d }_{ l } $$ On integrating the equation between limits when \(l = 0\) then \(I = { I }_{ 0 }\) and when \(l = l\) then \(I = { I }_{ t } \) $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = \int _{ 0 }^{ l }{ K'{ d }_{ l } } $$ $$ \int _{ { I }_{ 0 } }^{ { I }_{ t } }{ - \frac { { d }_{ i } }{ I } } = K'\int _{ 0 }^{ l }{ { d }_{ l } } $$ $$ - \ln { \frac { { I }_{ t } }{ { I }_{ 0 } } } = K'l $$ $$ \ln { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l $$ $$ \boxed { 2.303 \log { \frac { { I }_{ 0 } }{ { I }_{ t } } } = K'l } $$ Where \({ I }_{ o }\) is the intensity of incident radiation and \({ I }_{ t }\) is intensity of transmitted radiation. Equation is known as Lamberts Absorption Equation.