The term ‘lamp’ refers specifically to a light source, typically comprising a light-emitting element contained within an outer bulb or tube, which generally emits radiation within the visible spectrum.
The term is also used more widely to describe products such as table lamps and floor lamps, although these should more correctly be referred to as light fittings. Light fittings (or sometimes light fixtures) can comprise lamps, lampholders, control gear, housings and so on.
The term bulb may also be used to describe a lamp, although, more correctly, the bulb is the outer glass part of a lamp which contains the light source.
Lamps may include a reflector and a lens to control the beam angle (or beam spread), they may be dimmable, they can have a range of brightness, beam angle and colour, and can be used to provide direct or indirect light.
Lamp intensity (or power density) is the overall power output of a lamp across the entire electromagnetic spectrum, generally expressed in Watts (W). This is not a measure of the brightness of the lamp, as some of a lamp’s output may be in non-visible parts of the electromagnetic spectrum.
Lamp beam angle or beam spread is the angle of the cone of light emitted by reflectorised lamps, measured from the centre of the beam to the line where the intensity of the beam is 50% of the maximum.
Colour appearance refers to the visual sensation correlated with the ‘warmth’ or ‘coolness’ of the light emitted by a lamp.
 Types of lamp
There are a wide variety of different types of lamp available:
 Filament lamps
Filament lamps contain a tungsten wire (a filament) which is heated by an electrical current. Filament lamps may be incandescent lamps or halogen lamps.
 Incandescent lamps
Incandescent lamps contain a filament within a vacuum-sealed glass bulb. The passage of electrical current through the filament causes it to glow.
 Halogen lamps
Halogen lamps contain a coated filament surrounded by a halogen gas, which emits electrons when heated. They typically have a longer life and are more efficient than incandescent filament lamps.
Extra-low voltage lamps are small halogen lamps producing two or three times the light output of conventional filament lamps. They are typically powered from a separate 12 V source and have increased efficiency and lamp life. As the heating effect is lower, they can be preferable for display lighting
Discharge lamps, sometimes referred to as arc discharge lamps, discharge an electric current through a gas or gas / metal vapour mix. Discharge lamps may be fluorescent lamps or High Intensity Discharge (HID) lamps.
 Fluorescent Lamps.
Fluorescent lamps discharge an electric current through an inert gas and low pressure mercury vapour to produce ultraviolet (UV) energy. This generates ultraviolet radiation, which is converted into visible light by a phosphor coating on the inner face of the glass. The type of coating determines the spectrum of light emitted.
 Compact fluorescent lamps (CFL)
Compact fluorescent lamps are small diameter, single ended fluorescent lamps, bent to form a compact shape. They may have bases allowing them to be used as replacements for incandescent lamps.
 High intensity discharge lamps (HID)
High intensity discharge lamps are formed by compact arc tubes which enclose gas and metal salts. When the arc has formed, the metal salts evaporate, forming plasma which increases the intensity and reduces the power consumption of the arc. HID’s are typically mercury, metal halide (MH), ceramic metal halide (CMH) or high-pressure sodium (HPS).
 Xenon Arc Lamps
Xenon arc lamps contain xenon gas and emit light that is very similar to sunlight.
 Light-emitting diodes LED
LEDs contain solid semi-conductor materials that convert electrical impulses into light. They may include fluorescent materials that alter the colour of the light. They have a similar efficiency to CFL’s but are longer lasting.
 Related articles on Designing Buildings Wiki
- Architectural LED market.
- Ballast or control gear.
- Colour appearance.
- Dichroic reflector.
- Discharge lamp.
- Extra-low voltage lamps.
- General lighting v task lighting.
- Health and wellbeing impacts of natural and artificial lighting.
- Lamp efficacy.
- Light fitting.
- Lighting and energy efficiency.
- Lighting and health infographic.
- Lighting energy numeric indicator LENI.
- Lighting of construction sites.
- Luminaire efficacy.
- Luminous flux.
- Power factor.
- Space classifications for lighting controls.
- Specialist process lighting.
- The essential guide to retail lighting.
- The impact of lighting in retail design.
Featured articles and news
Four practical tips to bring sustainability into your building design.
Have a look at these designs for a new cross-laminated timber tower in Toronto.
Geniebelt examine the urgent need for change in construction.
Read our introductory article to the contractor's design portion.
Four ways in which smart cities could make our lives better.
Mayor Sadiq Khan announces new Greener City Fund in drive to make London the first 'National Park City'.
BSRIA announce UKAS accreditation for sound absorption testing.
The full terms of reference are published for the Grenfell Tower Inquiry.
Read our introductory article into the role and practice of the architect.
Despite dividing opinion since its 1955 completion, Stalin's gift to Poland, the PKiN, is still Warsaw's most recognisible landmark.
Graduate Engineer Brittany Harris asks, what makes a great place to work?
Mayor Sadiq Khan publishes new guidance aimed at fast-tracking affordable housing projects through planning.