Why is there a lampshade outside the lamp
Safety: because the light efficiency of the lamp is low, most turn to heat, easy to burn.
If it is a single wavelength of light, the color of the light that is reflected back, or through the lamp shade, will not change, but it will change the brightness and dimness.
Lamp light color won't change with lampshade, but after the light source to the lamp shade is reflected back to, or through the chimney of the light color will change (subjective visual), but in fact changed just different color contains ratio. Because of different wavelengths () the light reflectivity and transmissivity of different (to the lamp shade material).
Concentrated light: because the lamp is surrounded by the light, the light is wasted on the upward and the surrounding area, the lampshade is a concentrated beam of light.
