71.

A TV tower has a height of 100 m. What is the maximum distance up to which the TV transmission can be received (R = 8 × 10⁶ m) ?

• 34.77 km

• 32.70 km

• 40 km

• 40.70 km

A black body has maximum wavelength λ_m at 2000 K. Its corresponding wavelength at 3000 K will be

• $\frac{3}{2} {\mathrm{\lambda }}_{\mathrm{m}}$

• $\frac{2}{3} {\mathrm{\lambda }}_{\mathrm{m}}$

• $\frac{16}{81} {\mathrm{\lambda }}_{\mathrm{m}}$

• $\frac{81}{16} {\mathrm{\lambda }}_{\mathrm{m}}$