Physics

An open organ pipe supports standing waves with displacement antinodes at both ends, allowing both even and odd harmonics to be present in the sound produced.

Tungsten is used for bulb filaments because it has a very high melting point and good electrical resistance, making it ideal for glowing brightly without melting. The other materials either have lower melting points or are not suitable for filament use.

The fundamental frequency of a stationary wave in an open pipe is twice the fundamental frequency of a stationary wave in a closed pipe of the same length because an open pipe supports a full wavelength while a closed pipe supports only a quarter wavelength for the fundamental mode.

Copper is the best material for making connecting wires because it has excellent electrical conductivity, is relatively inexpensive, and is ductile, making it easy to draw into wires. While silver has slightly better conductivity, it is much more expensive and less commonly used for wiring.

The velocity of sound in dry air increases by approximately 0.6 m/s for each 1°C rise in temperature. This is a well-established physical fact and is commonly approximated as about 0.6 m/s per degree Celsius. Among the given options, 0.61 m/s (option C) is the closest and most accurate value. The originally marked answer (A: 1.61 m/s) is incorrect as it overestimates the increase by more than double.

A 40 W bulb uses 40 joules of energy per second. Over one hour (3600 seconds), the total energy converted to heat is 40 W × 3600 s = 144,000 J. This energy is primarily released as heat.

Projectile motion refers to the motion of an object thrown or projected into the air, subject only to gravity and air resistance. A gas-filled balloon does not follow a parabolic trajectory like projectiles; instead, it floats due to buoyant forces, so it is not an example of projectile motion.

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points, resulting in a straight line when voltage is plotted against current on a graph.

The resistance of a conductor depends on the nature of the conductor (material), its dimensions (length and cross-sectional area), and its physical state (such as temperature). Therefore, all the given factors affect resistance.

The Doppler effect is used to estimate the velocity of a star relative to Earth by observing the shift in the star's spectral lines. Interference and beats phenomena are related to wave behavior but are not used for measuring stellar velocities.