Diagram of a Lummer-Brodhun tively, falls on a diffuse white photometer head. surface W. Some of the light which is scattered bythis surface is reflected from the . The Lummer Brodhun Photometer finds wide application in comparison of illuminating power of different light sources. Our L.B. Photometer design and selection. 2 PRINCIPLES OF PHOTOMETRY. 3 LUMMER – BRODHUN PHOTOMETER. 4 PROBLEMS. PH UNIT- 3 LECT – 1. UNIT III LECT – 1. 2. PHOTOMETRY.
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A Lummer-Brodhun cube is made up of two right-angled prisms that are placed with their hypotenuse sides together to form a cube. April 1, Published: For a fuller description, see the following website. When the brightness are identical, the two circles become one. This Photometer consists of a metal box with two entrances and an eyepiece as well as a slot which allows a white magnesium carbonate disk to be mounted between the two entrances.
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112 – Lummer- Brodhun Photometer
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The photometer consists of an opaque screen which can be removed from a box. This item is a Lummer-Brodhun Photometer. Sc Practical Physics, pg Login or Create Account. In the box above the screen are two mirrors and a pair of prisms, which direct the light from the two light sources outside the box into the eyepiece at the top of the box.
OSA will be closed for the holidays from 21 December What the observer sees in the eyepiece is two superimposed circles on top of each other, one smaller than the other.
Some of the scattered light on each side is reflected by mirrors towards what is called a Lummer-Brodhun cube, which consists of two right-angled prisms. Equipment of Class Rooms.
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The observer can then see a circular disc of light from one source, surrounded by an halo from the other.
You may subscribe either as an OSA member, or as an authorized user of your institution. Light rays from the two sources enter on either side of the box. References You do not have subscription access to this journal. Click here to see what’s new. When this is accomplished, the luminosity of the unknown source can be calculated.
Lummer- Brodhun Photometer – Physics Museum – The University of Queensland, Australia
The light that is reflected off each side of the disk is directed through a right angled prism and towards a Lummer-Brodhun cube. Figure files are available to subscribers only. The yoke is attached to a brass rod for insertion into an optical bench or other equipment.
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Where the prisms do not touch, total internal reflection occurs. By llummer the unknown light source farther or closer to the photometer, one tries to get rid of the two distinct circles.
Where they do, all the light is transmitted to the other side. By matching the brightnesses of the two, the observer can use the known luminosity of one source and the distances to both sources to calculate the luminosity of the unknown source. Light from each of the two sources enters through its respective entrance and illuminates one photometsr of the white disk.
The housing is attached to a yoke on which it pivots. Not Accessible Your pphotometer may give you access. On either side of the screen are two large circular apertures in the sides of the box. Click here to learn more.
Cited by links are available to subscribers only. Similar to the Weber Photometer this item was designed to compare the brightness of an unknown light source to the brightness of a standard light source. The housing has no mechanism for adjusting the mirrors and is plain on the outside.
Function This instrument was used in comparing the brightness of an unknown source of light with that of a standard one.