Explanation

• The Doppler Effect is the change in the observed frequency of sound due to the relative motion between the source and the observer.
• If the source and observer move toward each other, the observed frequency increases.
• If they move away from each other, the observed frequency decreases.
• A common example is the changing pitch of an ambulance siren as it passes by.

Last verified on 02-09-2026

Explanation

• Ibn al-Haytham presented the theory of reflection and refraction of light.
• He is also known as Alhazen.
• His work, particularly his "Book of Optics", is titled Kitab al-Manazir, written during 1011–1021.
• Born: c. 965 (c. 354 AH) Basra, Buyid Emirate
• Died: c. 1040 (c. 430 AH)[1] (aged around 75) Cairo, Fatimid Caliphate

Last verified on 02-09-2026

Explanation

• Pressure is a scalar quantity.
• Pressure can be defined as the force acting per unit area.
• The unit of pressure is N/m² (Newton per square meter).
• It is also called a pascal (Pa).
• In SI base units: kg⋅m−1⋅s−2
• Derivation from other quantities: p = F / A
• Dimensional unit: M L^−1 T^-2.

Explanation

The particle's path is a helix.

Reasoning:

• Velocity has two components:
  • Parallel to the fields → electric force accelerates it along the axis
  • Perpendicular to the fields → magnetic force makes it circle around the axis
• Combined → helical path (with changing pitch as it speeds up/slows down)

Explanation

• Length, mass, and time are fundamental physical quantities.
• They can be measured using standard units.
• SI units are the metre for length, the kilogram for mass, and the second for time.