A galaxy is moving away from the Earth so that a spectral line at 6000 Å is observed at 6300 Å. Then the speed of the galaxy with respect to the Earth is
- 500 km/s
- 150 km/s
- 200 km/s
- 1500 km/s
The Correct Option is A
Solution and Explanation
The observed shift in wavelength \( \Delta \lambda = 6300 - 6000 = 300 \, \text{Å} \) is due to the Doppler effect.
The formula for the Doppler shift in wavelength for light is:
\( \Delta \lambda = \frac{v}{c} \lambda \)
where \( v \) is the velocity of the galaxy,
\( c \) is the speed of light, and
\( \lambda \) is the initial wavelength.
Substituting the known values, we calculate the speed of the galaxy as 500 km/s.
Top Questions on doppler effect
- When both the source of sound and observer approach each other with a speed equal to 10% of the speed of sound, then the percentage change in frequency heard by the observer is nearly
- AP EAPCET - 2025
- Physics
- doppler effect
- A passenger is sitting in a fast moving train. The engine of the train blows a whistle of frequency N. If the apparent frequency of sound heard by the passengers is \( N' \), then:
- MHT CET - 2025
- Physics
- doppler effect
- A source (S) of sound has frequency\( 240 Hz\). When the observer (O) and the source move towards each other at a speed \(v\) with respect to the ground (as shown in Case 1 in the figure), the observer measures the frequency of the sound to be \(288 Hz\). However, when the observer and the source move away from each other at the same speed v with respect to the ground (as shown in Case 2 in the figure), the observer measures the frequency of sound to be \(n\) Hz. The value of \(n\) is _____.
- JEE Advanced - 2024
- Physics
- doppler effect
- A train is moving with a speed of \(10 m/s\) towards a platform and blows a horn with frequency \(400 Hz\). Find the frequency heard by a passenger standing on the platform. Take speed of sound = \(310 m/s\).
- JEE Main - 2023
- Physics
- doppler effect
- A car P travelling at 20 \(ms^{–1}\) sounds its horn at a frequency of 400 Hz. Another car Q is travelling being the first car in the same direction with a velocity 40 \(ms^{–1}\) . The frequency heard by the passenger of the car Q is approximately [Take, velocity of sound = 360 \(ms^{–1}\) ]
- JEE Main - 2023
- Physics
- doppler effect
Questions Asked in KCET exam
- If the number of terms in the binomial expansion of \((2x + 3)^n\) is 22, then the value of \(n\) is:
- KCET - 2025
- Binomial theorem
- Which of the following statements is/are true about equilibrium?
- KCET - 2025
- Equilibrium
A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force \( F = 20 \, \text{N} \) acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take \( g = 10 \, \text{m/s}^2 \)):
- KCET - 2025
- work, energy and power
- A random experiment has five outcomes \(w_1, w_2, w_3, w_4, w_5\). The probabilities of the occurrence of the outcomes \(w_1, w_2, w_4, w_5\) are respectively \( \frac{1}{6}, a, b, \frac{1}{12} \) such that \(12a + 12b - 1 = 0\). Then the probabilities of occurrence of the outcome \(w_3\) is:
- KCET - 2025
- Probability
A wooden block of mass M lies on a rough floor. Another wooden block of the same mass is hanging from the point O through strings as shown in the figure. To achieve equilibrium, the coefficient of static friction between the block on the floor and the floor itself is
- KCET - 2025
- Newtons Laws of Motion
