In case the semiconductor substance is translucent, the light might be emitted from your junction as junction functions as the source of light-weight. LED is operated in forward biased manner only. If it can work in reverse biased it will get hurt mainly because it can't with stand reverse voltage. https://www.uk-exhibitionstands.co.uk/product-category/pop-ups-and-banner-stands/banner-stands/double-stand/