Image hover settings

Hi.
The below is the code for my image class where height and width of the image has been set to 100px.
When i hover on the image its background should change to black shadow(please find below for the code).
How to refer the hover property over an image, the below code does not work.please suggest is there alternate way to refer it.

.field-slideshow-slide, .field-slideshow-slide a, .field-slideshow-slide img {
cursor: pointer;
height: 100px;
width: 100px;
}
.field-slideshow-slide, .field-slideshow-slide a:hover, .field-slideshow-slide img:hover {
background: none repeat scroll 0 0 rgba(4, 4, 4, 0.65);
}