Answer
Verified
376.8k+ views
Hint: In the above question, the expression for the number of particles crossing a unit area perpendicular to X-axis in unit time is given. First we need to express the quantities in the given expression in terms of their dimensions. Further accordingly substituting them in the above expression will enable us to determine the dimensions of D.
Formula used:
$\text{A=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{\text{0}}} \right]$
$\text{V=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{3}}{{\text{T}}^{\text{0}}} \right]$
$\text{L=}\left[ {{\text{M}}^{\text{0}}}\text{L}{{\text{T}}^{\text{0}}} \right]$
$t=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{0}}\text{T} \right]$
Complete step-by-step solution:
In the above question it is given that ‘n’ is the number of particles crossing a unit area perpendicular to X-axis in unit time. The dimensions of area is $\text{A=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{\text{0}}} \right]$ and that of time is $\text{t=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{0}}\text{T} \right]$. Hence the dimension n(d)of n is equal to,
$\begin{align}
& n(d)=\dfrac{1}{A\times t} \\
& \Rightarrow n(d)=\dfrac{1}{\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{\text{0}}} \right]\times \left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{0}}\text{T} \right]} \\
& \therefore n(d)=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{-2}}}{{\text{T}}^{-1}} \right] \\
\end{align}$
The difference of a same physical quantity has the same dimension. In the question it is mentioned that ${{n}_{1}}$ and ${{n}_{2}}$ are the number of particles per unit volume. Hence the dimension ${{n}_{2}}-{{n}_{1}}(d)$ of ${{n}_{2}}-{{n}_{1}}$ is
$\begin{align}
& {{n}_{2}}-{{n}_{1}}(d)=\dfrac{1}{V} \\
& \Rightarrow {{n}_{2}}-{{n}_{1}}(d)=\dfrac{1}{\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{3}}{{\text{T}}^{\text{0}}} \right]} \\
& \therefore {{n}_{2}}-{{n}_{1}}(d)=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{-3}}{{\text{T}}^{\text{0}}} \right] \\
\end{align}$
Similarly the dimension ${{x}_{2}}-{{x}_{1}}(d)$ of ${{x}_{2}}-{{x}_{1}}$ is given by,
$\begin{align}
& {{x}_{2}}-{{x}_{1}}(d)=L \\
& \therefore {{x}_{2}}-{{x}_{1}}(d)=\text{L=}\left[ {{\text{M}}^{\text{0}}}\text{L}{{\text{T}}^{\text{0}}} \right] \\
\end{align}$
From the relation given in the question, the dimension D(d) of diffusion constant is equal to,
$n(d)=-D(d)\dfrac{{{n}_{2}}-{{n}_{1}}(d)}{{{x}_{2}}-{{x}_{1}}(d)}$
$\Rightarrow \left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{-2}}}{{\text{T}}^{-1}} \right]=-D(d)\dfrac{\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{-3}}{{\text{T}}^{\text{0}}} \right]}{\left[ {{\text{M}}^{\text{0}}}\text{L}{{\text{T}}^{\text{0}}} \right]}$
$\begin{align}
& \Rightarrow \left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{-2}}}{{\text{T}}^{-1}} \right]=-D(d)\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{-4}}{{\text{T}}^{\text{0}}} \right] \\
& \therefore D(d)=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{-1}} \right] \\
\end{align}$
Therefore the dimension of D are $\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{-1}} \right]$
Note: Number of particles is basically a constant. Hence it does not have any dimension. It is also to be noted that we have ignored the negative sign in the above relation given. This is because a negative sign can be considered as -1. Since -1 is nothing but a constant, hence it can be implied that it is dimensionless. It is also to be noted that the powers of the fundamental dimensions of the above physical quantities are added or subtracted using the laws of exponent.
Formula used:
$\text{A=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{\text{0}}} \right]$
$\text{V=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{3}}{{\text{T}}^{\text{0}}} \right]$
$\text{L=}\left[ {{\text{M}}^{\text{0}}}\text{L}{{\text{T}}^{\text{0}}} \right]$
$t=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{0}}\text{T} \right]$
Complete step-by-step solution:
In the above question it is given that ‘n’ is the number of particles crossing a unit area perpendicular to X-axis in unit time. The dimensions of area is $\text{A=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{\text{0}}} \right]$ and that of time is $\text{t=}\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{0}}\text{T} \right]$. Hence the dimension n(d)of n is equal to,
$\begin{align}
& n(d)=\dfrac{1}{A\times t} \\
& \Rightarrow n(d)=\dfrac{1}{\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{\text{0}}} \right]\times \left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{0}}\text{T} \right]} \\
& \therefore n(d)=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{-2}}}{{\text{T}}^{-1}} \right] \\
\end{align}$
The difference of a same physical quantity has the same dimension. In the question it is mentioned that ${{n}_{1}}$ and ${{n}_{2}}$ are the number of particles per unit volume. Hence the dimension ${{n}_{2}}-{{n}_{1}}(d)$ of ${{n}_{2}}-{{n}_{1}}$ is
$\begin{align}
& {{n}_{2}}-{{n}_{1}}(d)=\dfrac{1}{V} \\
& \Rightarrow {{n}_{2}}-{{n}_{1}}(d)=\dfrac{1}{\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{3}}{{\text{T}}^{\text{0}}} \right]} \\
& \therefore {{n}_{2}}-{{n}_{1}}(d)=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{-3}}{{\text{T}}^{\text{0}}} \right] \\
\end{align}$
Similarly the dimension ${{x}_{2}}-{{x}_{1}}(d)$ of ${{x}_{2}}-{{x}_{1}}$ is given by,
$\begin{align}
& {{x}_{2}}-{{x}_{1}}(d)=L \\
& \therefore {{x}_{2}}-{{x}_{1}}(d)=\text{L=}\left[ {{\text{M}}^{\text{0}}}\text{L}{{\text{T}}^{\text{0}}} \right] \\
\end{align}$
From the relation given in the question, the dimension D(d) of diffusion constant is equal to,
$n(d)=-D(d)\dfrac{{{n}_{2}}-{{n}_{1}}(d)}{{{x}_{2}}-{{x}_{1}}(d)}$
$\Rightarrow \left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{-2}}}{{\text{T}}^{-1}} \right]=-D(d)\dfrac{\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{-3}}{{\text{T}}^{\text{0}}} \right]}{\left[ {{\text{M}}^{\text{0}}}\text{L}{{\text{T}}^{\text{0}}} \right]}$
$\begin{align}
& \Rightarrow \left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{-2}}}{{\text{T}}^{-1}} \right]=-D(d)\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{-4}}{{\text{T}}^{\text{0}}} \right] \\
& \therefore D(d)=\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{-1}} \right] \\
\end{align}$
Therefore the dimension of D are $\left[ {{\text{M}}^{\text{0}}}{{\text{L}}^{\text{2}}}{{\text{T}}^{-1}} \right]$
Note: Number of particles is basically a constant. Hence it does not have any dimension. It is also to be noted that we have ignored the negative sign in the above relation given. This is because a negative sign can be considered as -1. Since -1 is nothing but a constant, hence it can be implied that it is dimensionless. It is also to be noted that the powers of the fundamental dimensions of the above physical quantities are added or subtracted using the laws of exponent.
Recently Updated Pages
How many sigma and pi bonds are present in HCequiv class 11 chemistry CBSE
Mark and label the given geoinformation on the outline class 11 social science CBSE
When people say No pun intended what does that mea class 8 english CBSE
Name the states which share their boundary with Indias class 9 social science CBSE
Give an account of the Northern Plains of India class 9 social science CBSE
Change the following sentences into negative and interrogative class 10 english CBSE
Trending doubts
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
The Equation xxx + 2 is Satisfied when x is Equal to Class 10 Maths
In Indian rupees 1 trillion is equal to how many c class 8 maths CBSE
Which are the Top 10 Largest Countries of the World?
How do you graph the function fx 4x class 9 maths CBSE
Give 10 examples for herbs , shrubs , climbers , creepers
Difference Between Plant Cell and Animal Cell
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
Why is there a time difference of about 5 hours between class 10 social science CBSE