POV-Ray : Documentation : Looks_like
  POV-Ray 3.6 Documentation Online View Shadowless Lights Projected_Through Looks_like

Normally the light source itself has no visible shape. The light simply radiates from an invisible point or area. You may give a light source any shape by adding a looks_like { OBJECT } statement.

There is an implied no_shadow attached to the looks_like object so that light is not blocked by the object. Without the automatic no_shadow the light inside the object would not escape. The object would, in effect, cast a shadow over everything.

If you want the attached object to block light then you should attach it with a union and not a looks_like as follows:

  union {
    light_source { <100, 200, -300> color White }
    object { My_Lamp_Shape }

Presumably parts of the lamp shade are transparent to let some light out. Shadowless Lights Projected_Through

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