\({g_h} = g\left( {1 - \frac{{2h}}{{{R_e}}}} \right)\)
Where \(R_e\) is radius of earth.
The acceleration due to gravity at a depth \(d\) is given as
\({g_d} = g\left( {1 - \frac{d}{{{R_e}}}} \right)\)
Given, \({g_h} = {g_d}\)
\(g\left( {1 - \frac{{2h}}{{{R_e}}}} \right) = g\left( {1 - \frac{d}{{{R_e}}}} \right)\)
\(d = 2h = 2 \times 1 = 2km\left( {h = 1\,km} \right)\)
[$g=\frac{G M}{R^{2}}=9.8 \,ms ^{-2}$ લો અને પૃથ્વીની ત્રિજ્યા $R =6400\, km$]