The ratio of the strengths of the four fundamental forces in nature,$F_{G}: F_{N}: F_{E}: F_{W}=$

Identify the pair of physical quantities which have different dimensions.

Which of the following statements is incorrect?

Give an example of:
$(a)$ a physical quantity which has a unit but no dimensions
$(b)$ a physical quantity which has neither unit nor dimensions
$(c)$ a constant which has a unit
$(d)$ a constant which has no unit

Which two of the following five physical parameters have the same dimensions $?$
$(1)$ energy density
$(2)$ refractive index
$(3)$ dielectric constant
$(4)$ Young's modulus
$(5)$ magnetic field

In an experiment of measuring the refractive index of a glass slab using a travelling microscope in a physics lab,a student measures the real thickness of the glass slab as $5.25\,mm$ and the apparent thickness of the glass slab as $5.00\,mm$. The travelling microscope has $20$ divisions in $1\,cm$ on the main scale,and $50$ divisions on the Vernier scale are equal to $49$ divisions on the main scale. The estimated uncertainty in the measurement of the refractive index of the slab is $\frac{x}{10} \times 10^{-3}$,where $x$ is $..............$