When we place a glass prism in the path of a narrow beam of white light a spectrum is obtained. What happens when a second identical prism is placed in an inverted position with respect to the first prism ? Draw a labelled ray diagram to illustrate it.

When a second identical glass prism is placed in an inverted position with respect to the first prism, the dispersed spectrum of seven colours enters the second prism. The second prism recombines all the colours to form a single beam of white light that emerges from its other side. This phenomenon is known as the recombination of the spectrum of white light.

Here is the labelled ray diagram illustrating this phenomenon:

``diagram {"xrange": [-40.4, 480.4], "yrange": [-242.2, -12.8], "polygons": [{"points": [[420.0, -80.0], [430.0, -80.0], [430.0, -170.0], [420.0, -170.0]]}], "lines": [{"from": [10.0, -150.0], "to": [80.0, -130.0], "label": ""}, {"from": [80.0, -130.0], "to": [125.0, -110.0], "label": ""}, {"from": [80.0, -130.0], "to": [115.0, -140.0], "label": ""}, {"from": [125.0, -110.0], "to": [275.0, -125.0], "label": ""}, {"from": [115.0, -140.0], "to": [285.0, -125.0], "label": ""}, {"from": [275.0, -125.0], "to": [325.0, -125.0], "label": ""}, {"from": [285.0, -125.0], "to": [325.0, -125.0], "label": ""}, {"from": [325.0, -125.0], "to": [420.0, -125.0], "label": ""}], "points": [{"x": 100.0, "y": -220.0, "label": ""}, {"x": 300.0, "y": -35.0, "label": ""}, {"x": 25.0, "y": -125.0, "label": ""}, {"x": 180.0, "y": -105.0, "label": ""}, {"x": 180.0, "y": -155.0, "label": ""}, {"x": 380.0, "y": -115.0, "label": ""}, {"x": 425.0, "y": -185.0, "label": ""}]} ``