Venus Temperature Explanation
The question asks why Venus has a lower effective radiating temperature than Earth, even though it receives more solar energy due to its closer proximity to the Sun.
Understanding Albedo
The key factor is albedo, which measures how much solar radiation a planet reflects back into space. A higher albedo means more reflection and less absorption of sunlight.
Venus's High Albedo
Venus possesses a thick atmosphere filled with clouds made primarily of sulfuric acid. These clouds are highly reflective.
- Venus's albedo is approximately 0.75 (or 75%).
- Earth's albedo is approximately 0.30 (or 30%).
This means Venus reflects significantly more sunlight (75%) than Earth (30%).
Impact on Temperature
Despite receiving more intense solar energy, Venus absorbs less of it because a large fraction is reflected away due to its high albedo. Consequently, its effective radiating temperature is lower than Earth's.
Evaluating Other Options
- Options 2 and 3 regarding negligible $CO_2$ or $N_2$ are incorrect. Venus's atmosphere is primarily carbon dioxide ($CO_2$), contributing to a strong greenhouse effect and high surface temperature, but the *effective radiating temperature* is influenced by overall energy balance, dominated by albedo in this scenario. Nitrogen ($N_2$) is not the primary factor determining planetary temperature regulation in this context.
- Option 1 (low albedo) would lead to higher temperatures, contrary to the observation.
Therefore, the high albedo of Venus is the reason for its lower effective radiating temperature compared to Earth.
Important Questions from Planetary Bodies
- The correct sequence of planets in order of increasing surface temperature is:
- Atmosphere of planet Mars is almost entirely made up of $\text{CO}_2$. But the surface temperature of Mars is less than that of the Earth because:
- Consider two planets A and B with radii $2r$ and $r$, respectively. Let their distances from the Sun be $d$ and $2d$, respectively. The solar constants for A ($F_{\text{SA}}$) and B ($F_{\text{SB}}$) are related by
- Consider two planets 'A' and 'B' with the following characteristics. The relationship between $T_1$ and $T_2$ is
Distance from the Sun Radius of the planet Incident Solar flux density Equivalent temperature Planet A $d_1$ $r_1$ $F_1$ $T_1$ Planet B $d_2 = 4d_1$ $r_2 = 2r_1$ $F_2$ $T_2$ A planet of radius $r$ has a core of radius $r_c$ and a mantle. It has no crust. Its mean density is $\rho$ and the density of its core is $\rho_c$. What is the density of the mantle?
