Question Details

A dimensionless quantity is constructed in terms of electronic charge 𝑒, permittivity of free space πœ€0, Planck’s constant β„Ž, and speed of light 𝑐. If the dimensionless quantity is written as π‘’π›Όπœ€0 π›½β„Žπ›Ύπ‘π›Ώ and 𝑛 is a non-zero integer, then (𝛼, 𝛽, 𝛾, 𝛿) is given by

Options

A

(2𝑛, βˆ’π‘›, βˆ’π‘›, βˆ’π‘›)

B

(𝑛, βˆ’π‘›, βˆ’2𝑛, βˆ’π‘›)

C

(𝑛, βˆ’π‘›, βˆ’π‘›, βˆ’2𝑛)

D

(2𝑛, βˆ’π‘›, βˆ’2𝑛, βˆ’2𝑛)

Show Answer

Correct Answer :

Option A

(2𝑛, βˆ’π‘›, βˆ’π‘›, βˆ’π‘›)

(2n, -n, -n, -n)

Solution :

The correct option is (2n, -n, -n, -n).

To find the values of Ξ±, οΏ½οΏ½, Ξ³, and Ξ΄ such that the quantity eΞ±Ξ΅0Ξ²hΞ³cΞ΄ is dimensionless, we can write down the dimensions of each fundamental quantity in terms of Mass (M), Length (L), Time (T), and Electric Current (A).

Let's find the dimensional formula for each parameter:
1. Electronic charge (e):
Charge is current multiplied by time.
[e]=A1T1

2. Permittivity of free space (Ξ΅0):
From Coulomb's Law, the electrostatic force between two charges is F=14πΡ0q2r2, which gives Ξ΅0=q24Ο€Fr2.
Thus, the dimensions of Ξ΅0 are:
[Ξ΅0]=A2T2(MLT-2)(L2)=M-1L-3T4A2

3. Planck’s constant (h):
From the relation E=hΞ½, where E is energy and Ξ½ is frequency:
[h]=[E][Ξ½]=ML2T-2T-1=ML2T-1

4. Speed of light (c):
[c]=LT-1

Now, we write the dimension of the given quantity:
[eΞ±Ξ΅0Ξ²hΞ³cΞ΄]=M0L0T0A0

Substituting the dimensional formulas, we get:
(AT)Ξ±(M-1L-3T4A2)Ξ²(ML2T-1)Ξ³(LT-1)Ξ΄=M0L0T0A0

Grouping the powers for each base unit:
Mass (M): -Ξ²+Ξ³=0β‡’Ξ²=Ξ³
Length (L): -3Ξ²+2Ξ³+Ξ΄=0
Time (T): Ξ±+4Ξ²-Ξ³-Ξ΄=0
Current (A): Ξ±+2Ξ²=0β‡’Ξ±=-2Ξ²

From Ξ²=Ξ³, let's substitute this into the equation for Length:
-3Ξ²+2Ξ²+Ξ΄=0β‡’-Ξ²+Ξ΄=0β‡’Ξ΄=Ξ²

Let's check the Time equation with these substitutions:
(-2Ξ²)+4Ξ²-Ξ²-Ξ²=0
This is consistent, meaning any non-zero value can be used as a scaling factor.

If we set Ξ²=-n (where n is a non-zero integer), we obtain:
Ξ±=-2Ξ²=2n
Ξ²=-n
Ξ³=Ξ²=-n
Ξ΄=Ξ²=-n

Therefore, the coordinates (Ξ±,Ξ²,Ξ³,Ξ΄) are given by (2n,-n,-n,-n).

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