The unit of luminous flux is:

• Lux

• Lumen

• Candela

• Watt

Answer explanation

The unit of luminous flux is the lumen, which measures the total amount of visible light emitted by a source. Lux measures illuminance, candela measures luminous intensity, and watt measures power.

Which law states that illumination on a surface is inversely proportional to the square of the distance from the source?

• Lambert’s Law

• Inverse Square Law

• Kirchhoff’s Law

• Stefan-Boltzmann Law

Answer explanation

The Inverse Square Law states that the intensity of illumination decreases with the square of the distance from the light source. This principle is fundamental in physics and applies to various fields, including optics.

The luminous intensity of a source is measured in:

• Lumen

• Lux

• Candela

• Foot-candle

Answer explanation

The luminous intensity of a source is measured in candela, which quantifies the amount of light emitted in a particular direction. Lumen measures total light output, lux measures illuminance, and foot-candle is a unit of illuminance as well.

Which device is used to measure the total luminous flux emitted by a light source?

• Goniophotometer

• Lux meter

• Spectrometer

• Integrating sphere

Answer explanation

An integrating sphere is used to measure the total luminous flux emitted by a light source by capturing all emitted light uniformly, making it the correct choice. Other devices serve different purposes.

Which of the following lamps has the highest luminous efficacy?

• Tungsten filament lamp

• Mercury vapor lamp

• Fluorescent tube

• LED lamp

Answer explanation

The LED lamp has the highest luminous efficacy among the options, converting a greater percentage of electrical energy into visible light compared to tungsten filament, mercury vapor, and fluorescent lamps.

Which of the following correctly matches the lamp type with its characteristic?

• Tungsten filament – long life, high efficiency

• Fluorescent lamp – flicker-free, no starter needed

• Mercury vapor lamp – requires warm-up time

• LED lamp – uses gas discharge

Answer explanation

The mercury vapor lamp requires warm-up time to reach full brightness, making this characteristic accurate. The other options incorrectly describe their respective lamp types.

Which of the following is a polar curve used in lighting design?

• A plot showing color spectrum of light

• A curve showing temperature vs. time

• A plot of luminous intensity in various directions

• A graph of voltage vs. current for a lamp

Answer explanation

The correct choice is a plot of luminous intensity in various directions, as it represents how light is distributed in space, which is essential in lighting design. Other options do not focus on directional light intensity.

According to BIS standards, which of the following is most important in flood lighting design?

• Voltage regulation

• Color temperature

• Uniform illumination and glare control

• Lamp base type

Answer explanation

Uniform illumination and glare control are crucial in flood lighting design to ensure safety and comfort. Proper distribution of light minimizes harsh shadows and reduces glare, enhancing visibility and overall effectiveness.

Which term refers to the amount of light falling on a surface?

• Luminous flux

• Illuminance

• Luminous efficacy

• Luminance

Answer explanation

The term 'illuminance' refers to the amount of light that falls on a surface, measured in lux. In contrast, 'luminous flux' measures total light output, 'luminous efficacy' relates to efficiency, and 'luminance' measures brightness.

Which of the following is a key advantage of LED lighting over traditional lighting methods?

• Requires ballast to operate

• Emits light in all directions

• High energy efficiency and long life

• Contains mercury vapor

Answer explanation

The key advantage of LED lighting is its high energy efficiency and long life, making it more cost-effective and environmentally friendly compared to traditional lighting methods.