for accessing image i am using below tag in visualforce page and i can able to see the image.

`<img src="{!$Asset.SLDS}/assets/icons/utility/chevrondown_60.png" />` 

for accessing image in the Lightning component i am using below tag but i can't able to see the image.

 `<img src="{!$Asset.SLDS+'/assets/icons/utility/chevrondown_60.png'}" />`

if anybody knows the how to access the image in the Lightning component help me (Spring 17).